Electrochemically active unit for an electrochemical device

Abstract

In order to provide an electrochemically active unit for an electrochemical device including a membrane electrode assembly, at least one gas diffusion layer and a seal that is linked to at least one of the at least one gas diffusion layers, in the manufacture whereof as even as possible a construction of the penetration region in which the gas diffusion layer of the electrochemically active unit is penetrated by the sealing material of the seal over the periphery of the gas diffusion layer is achievable, the seal includes a linking region, a distribution region and a connection region that connects the linking region and the distribution region to one another, wherein the connection region has a minimum height that is less than a quarter of the maximum height of the distribution region and less than a quarter of the maximum height of the linking region.

Claims

1. An electrochemically active unit for an electrochemical device, including a membrane electrode assembly, at least one gas diffusion layer and a seal extending in a longitudinal direction and a transverse direction and that is linked to at least one of the at least one gas diffusion layers, wherein the seal includes a linking region, a distribution region and a connection region that connects the linking region and the distribution region to one another, wherein the connection region has a minimum height in a lateral direction that is perpendicular to the longitudinal and transverse directions and that is less than a quarter of the maximum height of the distribution region and less than a quarter of the maximum height of the linking region, wherein the connection region has a varying cross-section around a perimeter of the at least one gas diffusion layer, wherein the connection region has thickened portions in which the connection region has a height that is greater than the minimum height of the connection region, and which are spaced from one another in the longitudinal direction of the connection region, wherein the connection region extends around the linking region in the longitudinal direction, and wherein the linking region is succeeded towards the outside of the seal by the connection region in the transverse direction of the seal that is oriented perpendicular to the longitudinal and lateral directions.

2. The electrochemically active unit according to claim 1, wherein the minimum height of the connection region is less than 0.3 mm.

3. The electrochemically active unit according to claim 1, wherein the connection region takes the form, at least in certain regions, of a flexible film.

4. The electrochemically active unit according to claim 1, wherein at least one of the thickened portions extends over the entire width of the connection region in a transverse direction of the connection region, perpendicular to the longitudinal direction of the connection region.

5. The electrochemically active unit according to claim 1, wherein the height of the thickened portions, the extent of each of the thickened portions in the longitudinal direction of the connection region, and/or the spacing between each pair of thickened portions succeeding one another in the longitudinal direction of the connection region varies in the longitudinal direction of the connection region.

6. The electrochemically active unit according to claim 1, wherein the seal has at least one sealing lip that forms a constituent part of the distribution region or a constituent part of the linking region.

7. The electrochemically active unit according to claim 1, wherein the seal has at least one deformation limiter that forms a constituent part of the distribution region or a constituent part of the linking region.

8. The electrochemically active unit according to claim 1, wherein the maximum height of the distribution region is at least 1.2 mm.

9. The electrochemically active unit according to claim 1, wherein the cross section of the distribution region varies in a longitudinal direction of the distribution region.

10. The electrochemically active unit according to claim 1, wherein the seal is injection molded and wherein the material of the seal penetrates part of at least one gas diffusion layer of the electrochemically active unit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a schematic plan view of an electrochemically active unit for an electrochemical device, which includes a membrane electrode assembly (not illustrated), at least one gas diffusion layer and a seal that is linked to at least one of the at least one gas diffusion layers;

(2) FIG. 2 shows a cross section of a detail, through the seal and the gas diffusion layer from FIG. 1, along the line 2-2 in FIG. 1, wherein it can be seen from the cross section that the seal includes: a linking region that penetrates part of the at least one gas diffusion layer of the electrochemically active unit; a distribution region that includes one or more sealing lips and/or a deformation limiter for the seal; and a connection region that connects the distribution region and the linking region to one another;

(3) FIG. 3 shows a plan view, corresponding to FIG. 1, of a second embodiment of an electrochemically active unit for an electrochemical device, in which the connection region of the seal has thickened portions that are spaced from one another in a longitudinal direction of the connection region; and

(4) FIG. 4 shows a cross section of a detail, corresponding to FIG. 2, through the seal and the at least one gas diffusion layer of the electrochemically active unit from FIG. 3, along the line 4-4 in FIG. 3, wherein it can be seen from the cross section that the seal includes: a linking region; a distribution region; and a connection region that connects the linking region and the distribution region to one another, wherein the connection region has thickened portions that are spaced from one another in a longitudinal direction of the connection region.

(5) Like or functionally equivalent elements are designated by the same reference numerals in all Figures.

DETAILED DESCRIPTION OF THE INVENTION

(6) An electrochemically active unit that is illustrated in FIGS. 1 and 2 and is designated 100 as a whole, for an electrochemical device (not illustrated as a whole), for example for a fuel cell stack or an electrolyzer, includes a membrane electrode assembly (not illustrated), at least one gas diffusion layer 102, and a seal 104 that extends in a longitudinal direction 106 of the seal 104, around the gas diffusion layer 102.

(7) As can best be seen from the cross section of FIG. 2, the seal 104 includes a linking region 108, a distribution region 110 that is remote from the gas diffusion layer 102, and a connection region 112 that connects the linking region 108 and the distribution region 110 to one another.

(8) The seal 104 is preferably made in one piece.

(9) The seal 104 is preferably injection molded.

(10) The seal 104 is preferably made from an elastomer material.

(11) The elastomer material preferably penetrates into the associated gas diffusion layer 102, with the result that the seal 104 is connected to the gas diffusion layer 102 by a substance-to-substance bond and/or by positive engagement.

(12) The outer edge region of the gas diffusion layer 102 into which the material of the seal 104 penetrates, and which thus forms a constituent part of the linking region 108, is marked by cross hatching in FIG. 2 and is designated a penetration region 114.

(13) The linking region 108 extends in a longitudinal direction 116, preferably in a closed ring, around the gas diffusion layer 102.

(14) The longitudinal direction 116 of the linking region 108 runs parallel to the longitudinal direction 106 of the seal 104 as a whole.

(15) The maximum height H.sub.A of the linking region 108 preferably corresponds at least to the height H.sub.G of the gas diffusion layer 102.

(16) In this description and the attached claims, the term “height” of an element is used to mean the extent of the respective element in a stack direction 118 of the electrochemical device, in which a plurality of electrochemically active units 100 are arranged one above the other in the direction of the stack.

(17) Together with a respective bipolar plate (not illustrated), an electrochemically active unit 100 may form an electrochemical cell of the electrochemical device.

(18) In that case, the electrochemical device includes a plurality of electrochemical cells, which are arranged one above the other in the stack direction 118, and preferably two end plates between which the stack of electrochemical cells is arranged and which are clamped towards one another by a clamping device (not illustrated) in order to act upon the electrochemical cells that are arranged in between, and in particular the electrochemically active units 100 thereof, with a clamping force applied in the stack direction 118.

(19) In a transverse direction 120 that is oriented perpendicular to the longitudinal direction 106 of the seal 104 and perpendicular to the stack direction 118, the linking region 108 is succeeded towards the outside by the connection region 112 of the seal 104.

(20) The connection region 112 preferably takes the form of a flexible film and has a minimum height h.sub.C that is less than a quarter of the maximum height H.sub.A of the linking region 108.

(21) The connection region 112 preferably takes a form that is substantially elastically deformable.

(22) The connection region 112 extends in a longitudinal direction 122 of the connection region 112, in the peripheral direction around the linking region 108, and preferably takes the form of a closed ring.

(23) The longitudinal direction 122 of the connection region 112 runs parallel to the longitudinal direction 106 of the seal 104 as a whole.

(24) Adjoining the connection region 112 in the transverse direction 120 towards the outside is the distribution region 110, which has one or more sealing lips 124.

(25) In the rest condition of the seal 104, that is to say in a relaxed condition in which the sealing lips 124 are not acted upon by a sealing force, the sealing lips 124 have a height H.sub.V which corresponds to the maximum height of the distribution region 110.

(26) If there are a plurality of sealing lips 124, the heights of these sealing lips 124 could also differ from one another in the relaxed condition, in which case the maximum height H.sub.V of these sealing lips 124 forms the maximum height H.sub.V of the distribution region 110.

(27) The sealing lips 124 extend in a longitudinal direction 126 of the distribution region 110, in the peripheral direction around the connection region 112 and the linking region 108, and preferably take the form of a closed ring.

(28) The longitudinal direction 126 of the distribution region 110 runs parallel to the longitudinal direction 106 of the seal 104 as a whole.

(29) If there are a plurality of sealing lips 124 in the distribution region 110, they are separated from one another by a respective lower intermediate region 128 that has a minimum height h.sub.Z.

(30) In order to limit the maximum deformation of the sealing lips 124, the distribution region 110 may further include a deformation limiter 130.

(31) The deformation limiter 130 is preferably arranged outside the sealing lips 124 (which are in particular in a closed ring) and has a height H.sub.S.

(32) The deformation limiter 130 preferably has a flattened top with a substantially planar stop surface 132.

(33) The deformation limiter 130 may extend in the longitudinal direction 126 of the distribution region 110, in the peripheral direction around the sealing lips 124, and preferably takes the form of a closed ring.

(34) The deformation limiter 130 is preferably separated from the single sealing lip 124 or from the sealing lip 124 furthest towards the outside by an intermediate region 134 that has a lower height than the sealing lip 124 and the deformation limiter 130.

(35) The intermediate region 134 has a minimum height h′.sub.Z, which may be the same size as the minimum height h.sub.Z of the intermediate region 128 between two sealing lips 124.

(36) However, the minimum height h′.sub.Z of the intermediate region 134 may also be greater or smaller than the minimum height h.sub.Z of the intermediate region 128.

(37) The minimum height h.sub.C of the connection region 112 is less than a quarter of the maximum height H.sub.V of the distribution region 110, with the result that the connection region 112 forms a constriction point between the distribution region 110 and the linking region 108 of the seal 104.

(38) Manufacture of the above-described seal 104 on the gas diffusion layer 102 is performed by an injection molding method, for example as follows:

(39) A first injection mold part (not illustrated) is placed by means of a compression edge on the gas diffusion layer 102, for example on the delimiting surface 136 of the gas diffusion layer 102 that is illustrated at the top in FIG. 2, and a second injection mold part (not illustrated) is brought into abutment against the respectively opposing delimiting surface 138 of the gas diffusion layer 102, illustrated at the bottom in FIG. 2, in order to serve as an arrester for compression of the gas diffusion layer 102 in the region of the compression edge of the first injection mold part, with the result that a cavity to be filled with the preferably elastomeric injection molding material or sealing material is formed between the two injection mold parts.

(40) The injection points for dispensing the injection molding material into the cavity are preferably arranged outside the deformation limiter 130, on plates provided separately for this purpose.

(41) When the cavity is subsequently filled with the injection molding material that is to be cured and from which the seal 104 is formed, the injection molding material first penetrates into the distribution region 110 at the outer edge of the seal 104, this distribution region 110 having a large cross section for throughflow—taken perpendicular to the longitudinal direction 126—that is for example from 1 mm.sup.2 to approximately 20 mm.sup.2.

(42) The heights h.sub.Z, h′.sub.Z, H.sub.S and H.sub.V of the different regions of the distribution region 110 are preferably in the range from approximately 0.5 mm to 2 mm.

(43) By contrast, the height h.sub.C of the connection region 112 is substantially smaller, and is preferably less than 0.3 mm, in particular less than 0.1 mm, particularly preferably less than 0.05 mm.

(44) The height h.sub.C of the connection region 112 may vary in the longitudinal direction 122 of the connection region 112, and thus over the periphery of the gas diffusion layer 102.

(45) Because of its small height, the connection region 112 has a significantly greater flow resistance to the injected injection molding material than the distribution region 110, and for this reason the injected injection molding material is first distributed in the distribution region 110 and only then penetrates through the connection region 112 and into the linking region 108.

(46) From the cavity, the injection molding material also penetrates into the edge region of the porous gas diffusion layer 102 that faces the cavity, with the result that the penetration region 114 of the gas diffusion layer 102 is penetrated by the material of the seal 104, and thus the linking region 108 of the seal 104 is connected to the gas diffusion layer 102 by a substance-to-substance bond and/or by positive engagement.

(47) In so doing, the seal 104 substantially entirely surrounds the outer surface 140 of the gas diffusion layer 102.

(48) After the injection molding material has cured to form the elastomeric sealing material and the injection mold parts have been removed, the arrangement of the seal 104 and the gas diffusion layer 102 takes the form shown in FIG. 2.

(49) The gas diffusion layer 102, with the seal 104 integrally formed thereon, can now be joined to a membrane electrode assembly and preferably to a further gas diffusion layer, which may likewise have a seal integrally formed thereon, to give the electrochemically active unit 100.

(50) The electrochemical device may in that case be composed of the electrochemically active units 100, which are arranged succeeding one another in the stack direction 118, bipolar plates arranged between them, and end plates arranged at the ends.

(51) A second embodiment of an electrochemically active unit 100, illustrated in FIGS. 3 and 4, differs from the first embodiment illustrated in FIGS. 1 and 2 in that the connection region 112 of the seal 104 has a plurality of thickened portions 142 that have a height H.sub.D exceeding the height h.sub.C of the sections of the connection region 112 in between.

(52) For example, it may be provided for the height H.sub.D to be at least three times the height h.sub.C.

(53) In particular, it may be provided for the height H.sub.D to be at least approximately 0.15 mm, preferably at least approximately 0.3 mm, particularly preferably at least approximately 0.90 mm.

(54) The thickened portions 142 are spaced from one another in the longitudinal direction 122 of the connection region 112.

(55) In particular, the spacing A.sub.D between two thickened portions 142 that succeed one another in the longitudinal direction 122 of the connection region 112 may be at least approximately 5 mm, in particular at least approximately 10 mm.

(56) The extent L.sub.D of a respective thickened portion 142 in the longitudinal direction 122 of the connection region 112 is preferably less than the spacing A.sub.D between two successive thickened portions 142 in the longitudinal direction 122 of the connection region 112.

(57) The thicker thickened portions 142 have the result of mechanical stabilizing the connection region 112, in particular when the seal 104 is demolded from the injection mold parts.

(58) Otherwise, the second embodiment of the electrochemically active unit 100 that is illustrated in FIGS. 3 and 4 corresponds, as regards its structure, functioning and mode of manufacture, to the first embodiment illustrated in FIGS. 1 and 2, so in this respect reference is made to the description thereof above.