WO2023227423A2

WO2023227423A2 - Electrochemical device and method for producing a sealing element on a gas diffusion layer of an electrochemical unit

Info

Publication number: WO2023227423A2
Application number: PCT/EP2023/063148
Authority: WO
Inventors: Jürgen KRAFT; Oliver Fink; Gerhard Schuller; Manuel Morcos; Michael Götz; Peter Stahl
Original assignee: Ekpo Fuel Cell Technologies Gmbh
Priority date: 2022-05-25
Filing date: 2023-05-16
Publication date: 2023-11-30
Also published as: DE102022113249A1

Abstract

To reduce local temperature rise in an edge web region of an electrochemical device comprising: a stack of multiple electrochemical units in succession along a stack direction, said units each comprising an electrochemically active membrane-electrode assembly; a bipolar plate and a sealing arrangement; at least one medium channel; at least one flow field through which a medium can flow from the medium channel to a different medium channel; and at least one communication channel through which the flow field and the medium channel are in fluid communication with one another, the communication channel comprising an edge web through which a flow of medium from the medium channel passes, where a coolant flows through a coolant channel separated from the interior of the edge web by a joining line, the flow field comprising an edge channel which is disposed between the edge web and the coolant channel and through which a flow of the medium from the medium channel passes, and where the sealing arrangement extends around the flow field and includes an inner edge which forms an edge of a cathode-side electrochemically active face or an anode-side electrochemically active face of the membrane-electrode assembly, the proposal is made for the inner edge of the sealing arrangement to lie on the side of the edge web that faces away from the medium channel.

Description

Electrochemical device and method for producing a sealing element on a gas diffusion layer of an electrochemical unit

The present invention relates to an electrochemical device which has a stack of several electrochemical units that follow each other along a stacking direction, each comprising an electrochemically active membrane-electrode arrangement, a bipolar plate and a sealing arrangement, at least one medium channel which extends through several along the stacking direction of the electrochemical units, at least one flow field through which a medium can flow from the medium channel transversely to the stacking direction from the medium channel to another medium channel, and at least one connecting channel through which the flow field and the medium channel are in fluid communication with one another, wherein the connecting channel comprises an edge web through which the medium from the medium channel flows during operation of the electrochemical device, wherein a coolant channel separated from the interior of the edge web by a joining line is flowed through by a coolant during operation of the electrochemical device, wherein the flow field forms an edge channel which is arranged between the edge web and the coolant channel and is flowed through by the medium from the medium channel during operation of the electrochemical device, and wherein the sealing arrangement extends along the circumferential direction of the flow field around the flow field and has an inner edge which has a cathode-side electrochemically active surface or an anode-side electrochemically active surface of the membrane-electrode arrangement. Such an electrochemical device can in particular be designed as a fuel cell device or as an electrolysis device.

If the connecting channel, through which a flow field and a medium channel are in fluid communication with one another, is not flowed through by a coolant during operation of the electrochemical device, but by another gas, for example an anode gas or a cathode gas of the electrochemical device, this supports the edge web The fluid medium flowing through does nothing to cool the areas of the membrane-electrode arrangement adjacent to the edge web. However, the electrochemical activity in these areas of the membrane-electrode arrangement is not lower than in other areas of the membrane-electrode arrangement, in particular not lower than in other areas of the membrane-electrode arrangement, which are arranged adjacent to an edge web forms part of a coolant connecting channel.

Due to the greater distance to the first coolant-carrying channel of the coolant flow field (corresponding to the first web within the adjacent gas flow field), during operation of the electrochemical device in an area of the membrane-electrode arrangement that is adjacent to an edge web that does not carry coolant, a locally higher temperature.

The present invention is based on the object of creating an electrochemical device of the type mentioned at the outset, in which a local temperature increase due to a lack of cooling in the area of an edge web of a connecting channel through which no coolant flows is avoided or at least reduced. This object is achieved according to the invention in an electrochemical device with the features of the preamble of claim 1 in that the inner edge of the sealing arrangement lies on the side of the edge web facing away from the medium channel.

This ensures that the sealing arrangement in the area of the connecting channel projects locally beyond the edge web into the area of the edge channel of the flow field.

As a result, an outer edge of the electrochemically active surface of the membrane-electrode arrangement is offset inwards, that is towards the center of the flow field, whereby the maximum distance from the outermost channel of the coolant flow field through which the coolant flows is reduced.

According to the invention, the sealing arrangement is preferably widened in the areas in which it crosses the connecting channels through which a coolant does not flow during operation of the electrochemical device.

Preferably, the sealing arrangement is widened in areas which extend along the circumferential direction of the sealing arrangement beyond the ends of the edge webs through which coolant does not flow.

To avoid temperature peaks, the sealing arrangement in the area of the connecting channels through which no coolant flows is locally extended into the area of the respectively assigned flow field.

In a preferred embodiment of the invention it is provided that the inner edge of the sealing arrangement lies on the side of the coolant channel facing the medium channel. Furthermore, it can be provided that the inner edge of the sealing arrangement lies in the area of the edge channel.

In a preferred embodiment of the invention it is provided that the connecting channel is formed between two bipolar plate layers, which are fixed to one another at the joining line.

The two bipolar plate layers can be fixed to one another in a materially bonded manner, in particular by welding, for example by laser welding.

In a preferred embodiment of the invention it is provided that the inner edge of the sealing arrangement lies on the side of the joining line facing away from the medium channel.

The inner edge of the sealing arrangement can be formed on a sealing element of the sealing arrangement, which is cohesively connected to a gas diffusion layer of the electrochemical unit in question.

The sealing element is preferably formed from an elastomeric material.

For example, it can be provided that the elastomer material of the sealing element penetrates a connection area of the gas diffusion layer.

Furthermore, it can be provided that the sealing element comprises a sealing projection which projects in the region of the connecting channel from a base body of the sealing element in a projection direction facing away from the medium channel.

Such a sealing projection preferably extends along the circumferential direction of the base body of the sealing element only over a part of the circumference of the base body of the sealing element. It is particularly favorable if the sealing projection extends along the circumferential direction of the base body of the sealing element over only less than 50%, particularly preferably over less than 25%, of the circumference of the base body of the sealing element.

In particular, the sealing projection preferably extends only over a part of the circumference of the base body of the sealing element, which crosses a connecting channel through which no coolant flows during operation of the electrochemical device.

The sealing projection can be locally interrupted.

The sealing projection can comprise a plurality of sections which are spaced apart from one another along the circumferential direction of the base body.

The extent (width) of the sealing projection perpendicular to its circumferential direction and perpendicular to the stacking direction is preferably greater than the extent (width) of the edge web of the flow field perpendicular to the circumferential direction and perpendicular to the stacking direction.

An extent (width) of the sealing arrangement perpendicular to its circumferential direction and perpendicular to the stacking direction is preferably larger in the area of the connecting channel than in at least one area outside the area of the connecting channel. This ensures that the size of the electrochemically active surface of the membrane-electrode arrangement is reduced only in the area of the connecting channel, in which the edge web is not flowed through by a coolant and therefore does not offer a sufficient cooling effect, while the electrochemically active surface of the membrane Electrode arrangement in the area of a connecting channel through which a coolant flows during operation of the electrochemical device, and is not unnecessarily reduced in the areas of the membrane-electrode arrangement lying outside the areas of the connecting channels. In a preferred embodiment of the invention it is provided that the sealing arrangement in the area of the connecting channel is provided with a plurality of recesses which are spaced apart from one another along the circumferential direction of the sealing arrangement and are formed on a sealing projection which is in the area of the connecting channel from a base body of the sealing element a projection direction facing away from the medium channel.

The sealing projection can form a passivation layer made of an elastomeric material, which is preferably molded onto a gas diffusion layer together with at least one sealing lip of the sealing arrangement.

The overspraying of the gas diffusion layer with a passivation layer made of elastomeric material on an area of the gas diffusion layer that is otherwise subject to high thermal stress ensures local reaction inactivity and thus a desired reduction in the thermal stress on the gas diffusion layer, which increases the durability of the electrochemical device during operation.

The elastomer material is injected onto the gas diffusion layer in a cavity of an injection molding tool. A connection area of the sealing element formed from the elastomeric material is created, in which porous material of the gas diffusion layer is at least partially penetrated by the elastomeric material.

If the gas diffusion layer can move freely in the connection area while the elastomer material is being introduced into the cavity of the injection molding tool, this can have the disadvantage that the gas diffusion layer floats on the elastomer material and one in the assembled one Electrochemical device of the membrane-electrode arrangement side of the gas diffusion layer is sprayed with elastomeric material, although this side of the gas diffusion layer should not be provided with elastomeric material.

Such “floating” of the gas diffusion layer can occur both in the area of the sealing projection and outside the area of the sealing projection. The side of the gas diffusion layer that faces the membrane-electrode arrangement and is not actually intended to be overmolded with elastomeric material can in particular be a side of the gas diffusion layer that has a microporous layer (MPL).

Through such a microporous layer, the elastomer material can only penetrate poorly or not at all into the gas diffusion layer, which results in a poor, undefined connection between the gas diffusion layer and the elastomer material. In addition, elastomer material contamination can form during such an overmolding process, which can endanger the later function of the electrochemical cell containing the overmolded gas diffusion layer and thus the later function of the electrochemical device.

The disadvantages described above of undesirable over-injection of the gas diffusion layer can be avoided if the injection molding tool comprises one or more deformation limiting elements which limit or prevent deformation of the gas diffusion layer during the introduction of the injection molding material into the cavity.

Such a deformation limiting element can be designed, for example, as a hold-down device. The deformation limiting element, for example in the form of a hold-down device, ensures that during the injection process the elastomer material introduced into the cavity of the injection molding tool preferably reaches the side of the gas diffusion layer facing away from the membrane-electrode arrangement during operation of the electrochemical device.

If the gas diffusion layer has a microporous layer (MPL) and a substrate, the elastomer material preferably ends up on the substrate side of the gas diffusion layer.

This ensures better penetration of the gas diffusion layer with the elastomer material and thus a better and more reliable connection of the sealing element formed from the elastomer material to the gas diffusion layer.

If the injection molding tool comprises at least one push-off tool part which has a push-off projection for pressing the gas diffusion layer during the injection molding process, the deformation limiting elements which are used in the area of the sealing projection are preferably spaced from the push-off projection of the push-off tool part.

As a result, the above-mentioned recesses are formed in the area of the sealing projection, which are preferably designed as passage openings in the sealing projection of the sealing element that extend through the sealing element.

These recesses, preferably in the form of passage openings, can in particular have a substantially circular cross section (taken perpendicular to the stacking direction of the electrochemical device). The sealing arrangement can also be provided in the at least one area outside the connecting channel and thus outside the sealing projection with a plurality of recesses which are spaced apart from one another along the circumferential direction of the sealing arrangement and are arranged on the inner edge of the sealing arrangement.

Such recesses are obtained if, when molding the sealing element, deformation limiting elements, for example hold-down devices, are used, which are arranged on a push-off projection of a push-off tool part of the injection molding tool or are formed in one piece with a push-off projection of the push-off tool part.

These deformation limiting elements in the non-passivated area lying outside the sealing projection weaken the connection between the sealing element formed from the elastomer material on the one hand and the gas diffusion layer on the other.

However, the geometry and position of the deformation limiting elements, for example in the form of hold-down devices, are selected so that a required minimum binding force is maintained.

Instead of a plurality of deformation limiting elements spaced apart along the circumferential direction of the gas diffusion layer, a deformation limiting element can also be used which comprises a wave-shaped outer edge. This results in the inner edge of the sealing arrangement formed from the elastomer material being wave-shaped in the at least one area outside the connecting channel in which no connecting projection is formed. It is advantageous if, in the non-passivated areas of the electrochemical device, which lie outside the area of the at least one sealing projection, a cathode-side sealing element is connected to the cathode-side gas diffusion layer with the same or a similar connection geometry as an anode-side sealing element to the anode-side gas diffusion layer .

If recesses are provided on the inner edge of the cathode-side sealing element and on the inner edge of the anode-side sealing element, they lie essentially congruent one above the other in the assembled state of the electrochemical device, preferably in the stacking direction of the electrochemical device.

Alternatively, it can be provided that an inner edge of the cathode-side sealing element, which borders the sealing element towards the center of the cathode-side gas diffusion layer, is moved further inwards, that is towards the center of the gas diffusion layer, than the inner edge of the anode-side sealing element.

For the connection of the sealing element to the gas diffusion layer, it is advantageous if the areas of the gas diffusion layer, which are in contact with a deformation limiting element of the injection molding tool during the introduction of the elastomeric material into the cavity of the injection molding tool, are essentially completely penetrated by the elastomeric material.

Alternatively, it can also be provided that these areas of the gas diffusion layer are only partially or not at all penetrated with elastomer material.

In the area of the at least one sealing projection, by means of which a passivated area of the electrochemical device is created, the deformation limiting elements, for example the hold-down devices, ensure a defined holding down of the gas diffusion layer while introducing the elastomer material into the cavity of the injection molding tool. Furthermore, the gas diffusion layer is precisely positioned relative to the sealing element formed from the elastomeric material during the injection molding of the elastomeric material.

The deformation limitation, in particular the holding down of the gas diffusion layer, can lead to a reduction in the thickness (expansion along the stacking direction) of the gas diffusion layer compared to the uncompressed state of the gas diffusion layer in the contact areas in which the gas diffusion layer is in contact with the deformation limiting elements, or in the vicinity thereof Lead contact areas. The result of this is that the cavity of the injection molding tool is better filled with elastomer material in the areas between the deformation limiting elements during the injection molding process. Alternatively, the height of the cavity of the injection molding tool can also be reduced in this area in order to reduce the overall height of the gas diffusion layer and sealing projection.

Preferably, the deformation limiting elements are arranged in the cavity of the injection molding tool on the same side of the gas diffusion layer on which the sealing projection is produced. It is particularly advantageous if this side is the substrate side of the gas diffusion layer, i.e. the side of the gas diffusion layer which faces away from the microporous layer (MPL) of the gas diffusion layer, since on the substrate side of the gas diffusion layer there is better penetration of the gas diffusion layer with the Elastomer material is guaranteed. This ensures a good connection of the sealing element made from the elastomer material to the gas diffusion layer.

It is advantageous if the gas diffusion layer is essentially completely penetrated by the elastomeric material in the areas in which it is in contact with the deformation limiting elements, because this also electrochemically deactivates the areas of the gas diffusion layer that are in contact with the deformation limiting elements, for example hold-down devices become. Alternatively, it can also be provided that the areas of the gas diffusion layer that are in contact with the deformation limiting elements are only partially or not at all penetrated by the elastomer material. This results in the areas of the gas diffusion layer that are in contact with the deformation limiting elements being partially electrochemically activated or completely electrochemically activated.

It is advantageous if the height of the edge web, the height of the web of the respective flow field closest to the edge web or the height of the edge web and the height of the web of the flow field closest to the edge web are in the area that (along the stacking direction) above or below the at least one sealing projection is reduced compared to the height of the edge web or the height of the web of the flow field closest to the edge web outside the area of the sealing projection. These local height reductions can be formed in one bipolar plate layer or in two bipolar plate layers.

These local height reductions serve to be able to produce a sufficiently high and easily produced sealing projection without increasing the local total height of an electrochemical cell (along the stacking direction). These local height reductions can also be carried out in an area adjacent to the area of the sealing projection to take assembly tolerances into account.

The size, shape, number, position and/or distance between the deformation limiting elements is preferably chosen so that there is an advantageous compromise between preventing the deformation of the gas diffusion layer on the one hand and a sufficient degree of filling of the cavity of the injection molding tool in the area of the sealing projection with the elastomeric material on the other hand. The medium that flows through the connecting channel during operation of the electrochemical device is preferably an anode gas (fuel gas, in particular containing hydrogen) or a cathode gas (oxidizing agent, in particular containing oxygen) of the electrochemical device.

In principle, the inner edge of the sealing arrangement, which is offset inwards, i.e. towards the center of the flow field, can be an inner edge of an anode-side region of the sealing arrangement or an inner edge of a cathode-side region of the sealing arrangement.

In a preferred embodiment of the invention it is provided that the inner edge of the sealing arrangement borders an electrochemically active surface of the membrane-electrode arrangement on the cathode side.

In another embodiment of the invention, it can be provided that the inner edge of the sealing arrangement borders an electrochemically active surface of the membrane-electrode arrangement on the cathode side and a further sealing arrangement is provided which borders an electrochemically active surface of the membrane-electrode arrangement on the anode side, whereby the inner edge of the cathode-side sealing arrangement lies on the side of the inner edge of the further anode-side sealing arrangement facing away from the medium channel.

In this case, a region of the cathode-side electrochemically active surface is always opposite a region of the anode-side electrochemically active surface of the membrane-electrode arrangement. There is then no area of the membrane-electrode unit that is supplied with oxidizing agent on the cathode side but is not also supplied with fuel gas on the anode side. This avoids locally increased aging of the membrane-electrode unit, which can occur if an area of the membrane-electrode unit is only supplied with oxidizing agent during operation of the electrochemical device, but not with fuel gas. In a particularly preferred embodiment of the electrochemical device, it is therefore also provided that an outer edge of a cathode-side electrochemically active surface of the membrane-electrode arrangement faces inward, that is to say, relative to an outer edge of an anode-side electrochemically active surface of the membrane-electrode arrangement towards the center of the flow field.

The electrochemical device according to the invention can in particular be designed as a polymer electrolyte membrane (PEM) fuel cell device, in which the membrane-electrode units of the electrochemical units of the electrochemical device each contain a polymer electrolyte membrane.

The present invention further relates to a method for producing a sealing element on a gas diffusion layer of an electrochemical unit, the method comprising the following:

Arranging an injection molding tool on the gas diffusion layer;

Introducing injection molding material into a cavity of the injection molding tool; wherein the sealing element comprises a sealing projection which projects from a base body of the sealing element in a projection direction pointing into an interior of the sealing element, wherein the sealing projection extends along the circumferential direction of the base body of the sealing element only over a part of the circumference of the base body of the sealing element. The present invention is based on the further object of creating a method of the type mentioned above, in which damage to the gas diffusion layer is avoided and a sealing element with a mechanically stable connection area for connection to the gas diffusion layer is produced.

This object is achieved according to the invention in a method with the features of the preamble of claim 18 in that the injection molding tool comprises at least one deformation limiting element which limits or prevents deformation of the gas diffusion layer during the introduction of the injection molding material into the cavity, the injection molding tool having at least one push-off element. Tool part comprises, which has a push-off projection for pressing the gas diffusion layer and wherein the at least one deformation limiting element is spaced from the push-off projection of the push-off tool part during the introduction of the injection molding material into the cavity of the injection molding tool.

The advantages of such an injection molding process have already been described above.

In a preferred embodiment of the method it is provided that the pressing projection of the pressing tool part has at least one rounding and/or at least one bevel.

In this way, damage to the component pressed between opposing push-off projections of the injection molding tool, in particular the gas diffusion layer, can be avoided. For the purpose of injecting a sealing element made of an elastomeric material onto a gas diffusion layer, the gas diffusion layer is inserted between two push-off projections of an injection molding tool and clamped and pressed when the injection molding tool is closed. The porous material of the gas diffusion layer is pressed to such an extent that the elastomer material introduced into the cavity of the injection molding tool does not penetrate the area of the gas diffusion layer lying between the pressing projections or only penetrates it to a very small extent, so that the central area of the gas diffusion layer surrounded by the pressing projections, i.e the part of the gas diffusion layer used in the electrochemical device for supplying cathode gas or anode gas to the membrane-electrode arrangement is only penetrated minimally.

Known push-off projections of injection molding tools have rectangular cross-sections that are easy to manufacture and are preferably designed to be mirror-symmetrical in relation to a plane aligned perpendicular to the stacking direction.

The use of such pressing projections can result in damage to the component pressed between the pressing projections, which can directly or indirectly cause damage to the electrochemical cell in which the gas diffusion layer is installed and thus cause failure of the entire fuel cell stack.

It is therefore important to ensure that the gas diffusion layer, onto which the sealing element made of an elastomeric material is to be molded, has no previous damage. Such prior damage can include, for example, fiber breaks in the gas diffusion layer, structural defects in a microporous layer (“MPL”) of the gas diffusion layer or, if the gas diffusion layer that is inserted into the injection molding tool is already provided with an electrode layer and a membrane, prior damage to the gas diffusion layer Membrane and/or leaks in the electrochemical cell. By designing at least one of the pressing projections with a geometry that deviates from the usual rectangular geometry, the load on the components pressed between the pressing projections in the contact area with the pressing projections is reduced.

This can be achieved by at least one of the pressing projections, preferably both pressing projections, having at least one rounded edge, a contact surface with a convexly curved region and/or at least one bevel.

It is particularly advantageous if the contact surface of the push-off projection only has small changes in direction on the scale of the pore size of the gas diffusion layer.

The pore size of the gas diffusion layer corresponds, for example, to the distance between the fibers of the gas diffusion layer.

For example, the change in height of the contact surface of the push-off projection is preferably no more than approximately one pore size over the length of half a pore size. The tangent on the contact surface of the push-off projection is therefore inclined relative to a plane perpendicular to the stacking direction (for example one of the main planes of the uncompressed gas diffusion layer) by an angle α of less than 60°, particularly preferably of less than 45°.

The total width of the push-off projection, that is to say its extent perpendicular to the stacking direction and perpendicular to the circumferential direction of the gas diffusion layer, is preferably a multiple of the pore size of the gas diffusion layer and is particularly preferably more than 0.5 mm, for example more than 1 mm. However, an overall width of the push-off projection that is too large leads to an undesirable reduction in the size of the electrochemically active region of the electrochemical device, since it increases the distance between the sealing structure of the sealing element and the electrochemically active region.

If the gas diffusion layer is designed asymmetrically, for example has a microporous layer (MPL) on one side or is provided on one side with a catalyst layer, a catalyst layer and a membrane or with a complete membrane-electrode arrangement, it can also make sense to design the pressing projections between which such an asymmetrical gas diffusion layer is pressed asymmetrically. Otherwise, a damaged microporous layer (MPL) of the gas diffusion layer would come into contact with a membrane-electrode assembly during assembly of the electrochemical device, which could cause damage to the membrane-electrode assembly.

For example, it can be provided that the push-off projection is completely eliminated on one side of the gas diffusion layer. This is preferably the side of the gas diffusion layer that is provided with a microporous layer (MPL), with a catalyst layer and/or with a membrane or with a complete membrane-electrode arrangement.

If one of the sides of the gas diffusion layer, for example a side which has a microporous layer (MPL), a catalyst layer, a membrane or a complete membrane-electrode arrangement, is particularly sensitive to handling, it can be advantageous if this side the gas diffusion layer is at least partially in contact with a contact element of the injection molding tool, which comprises an elastomeric material, during the introduction of the injection molding material into the cavity of the injection molding tool. Such a contact element can, for example, comprise a coating made of an elastomeric material on a region of the injection molding tool and/or a seal - preferably embedded without a groove, for example a flat seal, made of an elastomeric material, which is arranged in the injection molding tool.

A coating made of an elastomeric material can be produced, for example, by means of a pattern printing process, preferably a screen printing process or a pad printing process.

A seal made of an elastomeric material, which may be arranged in the injection molding tool, should be structured as little as possible in order not to produce any inhomogeneity in the load when the gas diffusion layer is pressed.

On the other hand, inserting a sealing cord with a circular cross-section into a groove that would leave gaps at its edges would not be advantageous.

An advantageous compression of the gas diffusion layer is achieved if the clear dimension between the push-off projections of the closed injection molding tool is smaller than the height (extension along the stacking direction) of the gas diffusion layer in the pressed fuel cell stack.

It has proven to be advantageous if the gas diffusion layer between the push-off projections of the injection molding tool is pressed to a maximum of 80%, particularly preferably to a maximum of 75%, of the thickness of the gas diffusion layer at a pressure of 0.025 MPa.

Furthermore, it has proven to be advantageous if the gas diffusion layer is pressed between the push-off projections of the injection molding tool to at least 40%, particularly preferably at least 50%, of the thickness of the gas diffusion layer at a pressure of 0.025 MPa. If a gas diffusion layer is provided with a catalyst layer, with a catalyst layer and a membrane or with a complete membrane-electrode arrangement, these additional layers can be produced separately from the gas diffusion layer and placed on the gas diffusion layer or laminated with the gas diffusion layer. Alternatively, it can also be provided that these additional layers are produced in situ on the gas diffusion layer.

Further features and advantages of the invention are the subject of the following description and the graphic representation of an exemplary embodiment. Shown in the drawings:

Fig. 1 is a perspective view of a section of a fuel cell stack of a fuel cell device in the area of a connecting channel, which connects a medium channel and a flow field of the fuel cell device, with two fuel cell units following one another in a stacking direction of the fuel cell stack of the fuel cell stack and a third bipolar plate lying above the two fuel cell units Fuel cell unit are shown;

FIG. 2 is a plan view from above along the stacking direction of the fuel cell stack onto the section of the fuel cell stack from FIG. 1;

Fig. 3 is an enlarged view of area I from Fig. 2;

4 shows a longitudinal section through the fuel cell stack from FIGS. 1 to 3, along line 4 - 4 in FIG. 3; 5 shows a perspective view of the section of the fuel cell stack corresponding to FIG. 1, with only the membrane-electrode arrangement and the sealing arrangement of a single fuel cell unit being shown;

6 is a top view along the stacking direction of the membrane-electrode arrangement and the sealing arrangement from FIG. 5;

7 shows a schematic section through an injection molding tool and a gas diffusion layer projecting into a cavity of the injection molding tool, the injection molding tool having a plurality of deformation limiting elements spaced apart from one another in a circumferential direction of the gas diffusion layer, which touch and come into contact with the gas diffusion layer before the injection molding material is introduced into the cavity of the injection molding tool with a push-off projection of a push-off tool part of the injection molding tool;

8 shows a partial top view from above of an assembly consisting of the gas diffusion layer and a sealing element fixed to the gas diffusion layer, which was produced by means of the injection molding tool from FIG. 7;

9 shows a schematic section through an injection molding tool, which comprises a plurality of deformation limiting elements, which are spaced apart from one another along the circumferential direction of the gas diffusion layer, are spaced from a push-off projection of a push-off tool part of the injection molding tool and touch the gas diffusion layer before the injection molding material is introduced into the cavity of the injection molding tool ; 10 shows a partial plan view of an assembly consisting of a gas diffusion layer and a sealing element fixed to the gas diffusion layer, which was produced by means of the injection molding tool shown in FIG. 9;

Fig. 11 shows a schematic section through an injection molding tool, a gas diffusion layer protruding into a cavity of the injection molding tool, which has a section pressed between two push-off projections of the injection molding tool, and a sealing element made of an elastomeric material which is molded onto the gas diffusion layer, the push-off projections being designed to be mirror-symmetrical to one another and one have a rectangular cross section;

Fig. 12 shows a schematic section through an injection molding tool, a gas diffusion layer protruding into a cavity of the injection molding tool, which has a section pressed between two push-off projections of the injection molding tool, and a sealing element made of an elastomeric material which is molded onto the gas diffusion layer, the push-off projections each having a convexly curved contact surface ;

Fig. 13 shows a schematic section through an injection molding tool, a gas diffusion layer protruding into a cavity of the injection molding tool, which has a section pressed between a push-off projection of a push-off tool part of the injection molding tool and a flat section of a further tool part of the injection molding tool, and a sealing element molded onto the gas diffusion layer made of an elastomeric material, wherein the push-off projection of the push-off tool part of the injection molding tool has a convexly curved contact surface; 14 shows a schematic section through an injection molding tool, a gas diffusion layer protruding into a cavity of the injection molding tool, which has a section pressed between two push-off projections of the injection molding tool, and a sealing element made of an elastomeric material which is molded onto the gas diffusion layer, the two push-off projections of the injection molding tool being designed asymmetrically to one another are, both push-off projections have a convex contact surface and the push-off projections protrude to different extents into the material of the gas diffusion layer;

15 shows a schematic section through an injection molding tool, a gas diffusion layer protruding into a cavity of the injection molding tool, which has a section pressed between two push-off projections of the injection mold, and a sealing element made of an elastomeric material which is molded onto the gas diffusion layer, the two push-off projections each having a contact surface, which have a section parallel to a main surface of the gas diffusion layer and each section inclined relative to a main surface of the gas diffusion layer, the push-off projections being designed asymmetrically to one another and one of the push-off projections penetrating further into the material of the gas diffusion layer than the other push-off projection;

16 shows a schematic section through an injection molding tool, a gas diffusion layer protruding into a cavity of the injection molding tool, which has a section pressed between a push-off projection of a push-off tool part of the injection molding tool on the one hand and an elastic contact element of the injection molding tool on the other hand, and a sealing element molded onto the gas diffusion layer one Elastomeric material, wherein the push-off projection of the push-off tool part of the injection molding tool has a convexly curved contact surface and a section of another tool part of the injection molding tool opposite the push-off projection of the push-off tool part is provided with a coating made of an elastomeric material; and

Fig. 17 shows a schematic section through a tool part of an injection molding tool, which is provided with a contact element for pressing a section of a gas diffusion layer, the contact element being designed as a separate sealing element which has one or more sealing lips and one formed on the tool part of the injection molding tool Groove is inserted.

Identical or functionally equivalent elements are designated with the same reference numerals in all figures.

1 to 6, designated as a whole by 100, for example a fuel cell device 102 or an electrolyzer, comprises a stack 104 of electrochemical units 106, for example fuel cell units 108 or electrolyzer units, the stack 104 having several in one stacking direction 110 successive electrochemical units 106 and a clamping device (not shown) for applying a clamping force directed along the stacking direction 110 to the electrochemical units 106.

As can best be seen from the sectional view in FIG. 4, each electrochemical unit 106 of the electrochemical device 100 includes a bipolar plate 112 and a membrane electrode assembly (MEA) 114. The membrane-electrode arrangement 114 comprises, for example, a catalyst-coated membrane (“Catalyst Coated Membrane”; CCM) and two gas diffusion layers 116 and 118, the first gas diffusion layer 116 being arranged, for example, on the anode side and the second gas diffusion layer 118, for example, being arranged on the cathode side.

The bipolar plate 112 is formed, for example, from a metallic material.

The bipolar plate 112 has a plurality of medium passage openings 120, through which a fluid medium to be supplied to the electrochemical device 100 (in the case of a fuel cell stack, for example a fuel gas or anode gas, an oxidizing agent or cathode gas or a coolant) can pass through the bipolar plate 112. The medium passage openings 120 of the bipolar plates 112 successive in the stack 104 and the spaces lying between the medium passage openings 120 in the stacking direction 110 together each form a medium channel 122.

Each medium channel 122, through which a fluid medium can be supplied to the electrochemical device 100, is assigned at least one other medium channel 122, through which the relevant fluid medium can be removed from the electrochemical device 100.

Through an intermediate flow field 124, which is preferably formed on a surface of an adjacent bipolar plate 112 or (for example in the case of a coolant flow field) in the space between the layers of a multi-layer bipolar plate 112, the medium can flow out of the first medium channel 122 transversely, preferably substantially flow perpendicularly to the stacking direction 110 through the respective flow field 124 to the second medium channel 122. 4 shows, for example, an anode gas medium channel 126 for an anode gas of the electrochemical device 100.

Each medium channel 122 is in fluid communication with the respectively assigned flow fields 124 through at least one connecting channel 128.

In the embodiment shown in the drawing, each bipolar plate 112 comprises a first bipolar plate layer 130 and a second bipolar plate layer 132, which are fixed to one another in a fluid-tight manner along connecting lines 134, which run perpendicular to the plane of the drawing in FIG. 4, preferably in a materially bonded manner, in particular by welding, for example by laser welding .

4, the anode gas medium channel 126 is in fluid communication with a flow field 138 for the anode gas via an anode gas connection channel 136, which is formed by a gap between the first bipolar plate layer 130 and the second bipolar plate layer 132 in which only one edge channel 140 is shown. This edge channel 140 forms the outermost channel of the flow field 138, is open to the membrane-electrode arrangement 114 and is delimited on its outer side facing the medium channel 122 by an edge web 142, which lies sealingly against the membrane-electrode arrangement 114.

During operation of the electrochemical device 100, the medium flows from the medium channel 122 through the connecting channel 128 into the interior 144 of the edge web 142, from where it passes through passage openings 145 through the flank 146 of the edge web 142 separating the interior 144 of the edge web 142 from the edge channel 140 enters the edge channel 140. A coolant channel 148, through which a coolant flows during operation of the electrochemical device 100 and is formed between the first bipolar plate layer 130 and the second bipolar plate layer 132 of a bipolar plate 112, is separated from the interior 144 of the edge web 142 by a joining line 134, which first bipolar plate layer 130 and the second bipolar plate layer 132 connects together.

An undesirable escape of the fluid media from the flow fields 124 of the electrochemical device 100 is prevented by a sealing arrangement 150, which extends along the circumferential direction 152 of the flow fields 124 around the flow fields 124 and two inner edges 155, namely an anode-side inner edge 154 and one cathode-side inner edge 156.

The anode-side inner edge 154 of the sealing arrangement 150 delimits an anode-side electrochemically active surface 158 of the membrane-electrode arrangement 114, and the cathode-side inner edge 156 of the sealing arrangement 150 delimits a cathode-side electrochemically active surface 160 of the membrane-electrode arrangement 114.

4, the sealing arrangement 150 preferably comprises two sealing elements 161, with a first sealing element 162 preferably on the anode-side gas diffusion layer 116 and a second sealing element 164 preferably on the cathode-side second gas diffusion layer 118 of the membrane-electrode arrangement 114 is fixed.

For example, it can be provided that the sealing elements 162 and 164 are molded or cast onto the respectively assigned gas diffusion layer 116 or 118. The first sealing element 162 preferably has one or more sealing lips 166, with which the first sealing element 164 rests in a fluid-tight manner on the first bipolar plate layer 130 of an adjacent bipolar plate 112.

The first sealing element 162 can also have further sealing lips 168, with which the first sealing element 162 rests in a fluid-tight manner on the first bipolar plate layer 130 of a first adjacent bipolar plate layer 112 and on the second bipolar plate layer 132 of a second adjacent bipolar plate 112, around a medium channel section 170 of the sealing arrangement 150, which extends around a medium channel 122 of the electrochemical device 100, so that an escape of medium from the medium channel 122 into the environment of the electrochemical device 100 and / or flow fields 124 of the electrochemical device 100 associated with other media is prevented.

The second sealing element 164 preferably has one or more sealing lips 166, with which the second sealing element 164 rests in a fluid-tight manner on the second bipolar plate layer 132 of an adjacent bipolar plate 112.

The sealing elements 162 and 164 of the seal assembly 150 are preferably formed from an elastomeric material.

This elastomer material preferably also penetrates the areas of the first gas diffusion layer 116 and the second gas diffusion layer 118 adjacent to the sealing elements 162 and 164, respectively, so that the gas diffusion layers 116 and 118 are not porous in these penetration areas, but are not penetrated by either the anode gas or the cathode gas can be.

The anode-side inner edge 154 of the sealing arrangement 150 is arranged on the side of an edge web 142 of a bipolar plate 112 facing the medium channel 122. If now the cathode-side inner edge 156 If the sealing arrangement 150 were arranged on the side of an edge web 142 of a bipolar plate 112 facing the medium channel 122, as is the case with known electrochemical devices 100, both the cathode-side electrochemically active surface 160 and the anode-side electrochemically active surface 158 of the membrane would be Electrode arrangement 114 extend into the area of the membrane electrode arrangement 114, which lies between the edge webs 142 and the medium channel 122.

However, the outer edge region of these electrochemically active surfaces 158, 160 would be so far away from the outermost coolant channel 148 that sufficient cooling of this outer edge region by the coolant flowing through the coolant channel 148 would not be guaranteed, so that the temperature of the electrochemical Device 100 would increase locally in this outer edge region of the membrane-electrode arrangement 114.

In order to solve this problem of a local temperature increase during operation of the electrochemical device 100, the sealing arrangement 150 in the embodiment of an electrochemical device 100 shown in the drawing is designed such that the cathode-side inner edge 156 of the sealing arrangement 150 is on the side of the edge web 142 facing away from the medium channel 122 lies.

This ensures that, during operation of the electrochemical device 100, electrochemical activity does not take place in the outer edge region of the membrane-electrode arrangement 114, which lies between the edge webs 142 and the medium channel 122, but only in the region of the membrane located further inside -Electrode arrangement 114, which adjoins the edge channels 140 and is therefore closer to the coolant channels 148. The outermost edge of the membrane-electrode arrangement 114, which shows electrochemical activity during operation of the electrochemical device 100, is thus shifted inwards in the embodiment of an electrochemical device 100 shown in the drawing, that is to say towards the center of the flow fields 124, whereby the maximum distance of an electrochemically active region of the membrane electrode arrangement 114 from the channels of the coolant flow field is reduced.

How far the cathode-side inner edge 156 of the sealing arrangement 150 is moved inwards, towards the center of the flow fields 124, depends on the geometric structure of the sealing arrangement 150 and the bipolar plate 112 in this area as well as on the extent of the connection area of the sealing arrangement 150, in which the elastomer material of the sealing arrangement 150 penetrates the adjacent gas diffusion layers 116 and 118, and on the desired temperature distribution, which in turn depends on the width of the edge channels 140 and the coolant channels 148 as well as on the thermal conductivity of the materials of the membrane-electrode arrangement 114 and the bipolar plates 112 depends. The occurrence of pressure peaks due to the extension of the seal arrangement 150 towards the center of the flow fields 124 should be avoided.

By extending the sealing arrangement 150 in the area of a connecting channel 128 beyond the positions of the edge webs 142 of the bipolar plates 112 inwards, towards the center of the flow fields 124, local temperature peaks during operation of the electrochemical device 100 can be effectively avoided.

Preferably, the cathode-side inner edge 156 of the sealing arrangement 150 lies on the side of the coolant channel 148 facing the medium channel 122. Furthermore, it is favorable if the cathode-side inner edge 156 of the sealing arrangement 150 lies in the area of the edge channel 140.

It is also advantageous if the cathode-side inner edge 156 of the sealing arrangement 150 lies on the side of the joining line 134 facing away from the medium channel 122, on which the first bipolar plate layer 130 and the second bipolar plate layer 132 of a bipolar plate 112 are fixed to one another.

Outside the area of the connecting channels 128 for the anode gas or for the cathode gas, through which the anode gas or the cathode gas flows from their respective medium channels 122 into the respectively assigned flow fields 124 or flows from the respective flow fields 124 into the respectively assigned medium channels 122 form the Interior spaces 144 of the edge webs 142 of the bipolar plates 112 are not components of such connecting channels 128, but are flowed through by coolant. Therefore, the problem explained above of locally inadequate cooling in the vicinity of the edge webs 142 only exists where the connecting channels 128 for anode gas or cathode gas are located.

The cathode-side inner edge 156 of the sealing arrangement 150 therefore only has to be laid on the side of the edge webs 142 facing away from a medium channel 122 where these connecting channels 128 for anode gas or cathode gas are located.

Where no such connecting channels 128 run, the cathode-side inner edge 156 of the sealing arrangement 150 can, however, lie on the side of the edge webs 142 facing the respective medium channel 122, whereby the available electrochemically active surface of the membrane electrode arrangements 114 in the areas is enlarged outside the connecting channels 128 for anode gas and cathode gas. In the embodiment of an electrochemical device 100 shown in the drawing, it is therefore provided that the cathode-side inner edge 156 of the sealing arrangement 150 is provided on a sealing projection 172 of the second sealing element 164, the sealing projection 172 being in the area of a connecting channel 128 of a base body 174 of the second sealing element 164 protrudes in a projection direction 176 facing away from the medium channel (see FIGS. 5 and 6).

If the circumferential direction of the flow fields 124 varies in the area of the connecting channel 128, as is the case in particular in corner areas of the flow fields 124, the projection direction 176 can have locally different orientations (see FIGS. 5 and 6).

The sealing projection 172 extends along the circumferential direction of the base body 174 of the first sealing element 162 only over a part of the circumference of the base body 174 of the first sealing element 162, preferably over less than 50% of the circumference of the base body 174 of the first sealing element 162, particularly preferably over less than 25% of the circumference of the base body 174 of the first sealing element 162.

The extent (width B) of the sealing projection 172 perpendicular to its circumferential direction and perpendicular to the stacking direction 110 is preferably greater than the extent (width b) of an edge web 142 perpendicular to its circumferential direction and perpendicular to the stacking direction 110.

The width B of the sealing projection 172, taken perpendicular to the circumferential direction of the sealing projection 172, is therefore greater than the width b of the edge web 142, taken perpendicular to the circumferential direction of an edge web 142. Due to the presence of the sealing projection 172, the extent of the sealing arrangement 150 perpendicular to its circumferential direction is greater in the area of at least one connecting channel 128 than in at least one area outside the area of the connecting channel.

In a variant of the embodiment of an electrochemical device 100 shown in FIGS. 1 to 6, it is provided that the sealing arrangement 150 is provided with a plurality of recesses 182 in the at least one area outside the connecting channel 128 and thus outside the sealing projection 172, which are along the circumferential direction 134 of the seal assembly 150 are spaced apart from one another and are arranged on the inner edge 155 of the seal assembly 150, as shown in FIG.

Such recesses 182 are obtained if, when molding the sealing element 161, deformation limiting elements, for example hold-down devices 186, are used, which are arranged on a pressing projection 188 of a pressing tool part 190 of an injection molding tool 192, in which the process of molding the sealing element 161 made of the elastomer material takes place the gas diffusion layer 116 or 118 is carried out.

Alternatively, it can be provided that at least one of the deformation limiting elements 184 is formed in one piece with the pressing projection 188 of the pressing tool part 190.

Such an injection molding tool 192 is shown schematically in FIG. 7.

The injection molding tool 192 is designed in several parts and includes a pressing tool part 190 and a supporting tool part 194. The push-off tool part 190 and the support tool part 194 together enclose a cavity 196 into which an injection molding material, preferably a starting material for an elastomer material, is introduced in a flowable state during the injection molding process.

The gas diffusion layer 116, 118 projects into this cavity 196.

The pressing tool part 190 has the pressing projection 188, which is provided with a pressing edge 198.

The gas diffusion layer 116, 118 inserted into the injection molding tool 192, which is mechanically compressible in its thickness direction 200 (in the assembled state of the electrochemical device 100 parallel to the stacking direction 110 of the electrochemical device 100), is locally compressed by means of the pressing projection 188 and the opposite support tool part 194 pressed. As a result, the capillary pressure in the pores of the porous gas diffusion layer 116, 118 increases locally, and the penetration of the gas diffusion layer 116, 118 with the injection molding material is limited in the x and y directions perpendicular to the thickness direction (z direction).

When producing the sealing element 161 by means of an injection molding process in the injection mold 192, very high injection pressures occur in the cavity 196 of the injection mold 192.

If the injection point or injection points through which the injection molding material is introduced into the cavity 196 lie outside the connection areas between the sealing element 161 and the gas diffusion layer 116, 118, it can occur during the filling of the cavity 196 of the injection molding tool 192 with the injection molding material in these connection areas the gas diffusion layer 116, 118 can be deformed. Through this deformation process, the gas diffusion layer 116, 118 is locally brought out of its original flat shape and subjected to bending.

Due to the bending of the gas diffusion layer 116, 118 in the deformed connection area, the gas diffusion layer 116, 118 can be damaged, for example by breaking.

In addition, if the gas diffusion layer 116, 118 is strongly bent, the connection area can be mechanically weakened by the gas diffusion layer 116, 118 protruding into the connection area 202, which is located above the gas diffusion layer 116, 118 in the thickness direction 200, which is also referred to as the connection lip 204, and so on prevents the flow of (especially elastomeric) injection molding material in this area.

It is then not guaranteed that the cavity 196 of the injection molding tool 192 in the area of the connecting lip 204 is completely filled, which increases the risk of mechanical damage to the connecting area 202 of the sealing element 161, in particular due to crack formation.

After the injection molding material has been introduced into the cavity 196 of the injection molding tool 192 and the injection molding material has hardened to form the sealing material of the sealing element 161, the sealing element 161 is produced on the gas diffusion layer 116, 118 and thus the formation of an assembly 206 which forms the gas diffusion layer 116, 118 and which includes the sealing element 161 fixed to the gas diffusion layer 116, 118 and is also referred to as seal-on GDL unit 208.

After opening the injection mold 192 by removing the push-off tool part 190 from the support tool part 194, the assembly 206 can be used in the assembly of the membrane-electrode assembly 114 and the assembly of the electrochemical device 100. The sealing element 161 of the finished assembly 206 comprises a sealing area 210 with a sealing lip 212, a penetration area 214 in which the injection molding material has penetrated into the porous material of the gas diffusion layer 116, 118 and which extends inwards from an outer edge 216 of the gas diffusion layer 116, 118 extends into the area of the push-off edge 198, and a connection region 202 in the form of a connection lip 204 lying outside the gas diffusion layer 116, 118, in the thickness direction 200 above and/or below the gas diffusion layer 116, 118.

In order to prevent the above-described deformation process on the gas diffusion layer 116, 118 when the injection molding material is introduced into the cavity 196 of the injection mold 192, a plurality of deformation limiting elements 184 are provided in the cavity 196 of the injection mold 192, which are in a parallel to the outer edge 216 of the gas diffusion layer 116, 118 and are spaced apart from one another in the circumferential direction 152 of the gas diffusion layer 116, 118 aligned parallel to the pressing edge 198 of the pressing tool part 190.

In the exemplary embodiment shown, the deformation limiting elements 184 are formed separately from the push-off tool part 190 and separately from the support tool part 190 of the injection molding tool 192.

In principle, the deformation limiting elements 184 can also be formed in one piece with another component of the injection molding tool 192, for example with the push-off tool part 190 or with the support tool part 194.

7, the deformation limiting elements 184 are in contact with the pressing projection 188 of the pressing tool part 190. Furthermore, the deformation limiting elements 184 touch the gas diffusion layer 116, 118 on the main surface 218 facing the push-off edge 198 even before the injection molding material is introduced into the cavity 196 of the injection mold 192.

An outer edge 220 of each deformation limiting element 184 facing away from the push-off edge 198 is arranged between the outer edge 216 of the gas diffusion layer 116, 118 on the one hand and the push-off edge 198 of the injection molding tool 192 on the other hand, so that the deformation limiting elements 184 cover the region of the gas diffusion protruding into the cavity 196 of the injection molding tool 192 location 116 , 118 do not completely cover.

The deformation limiting elements 184 arranged in the connection area between the gas diffusion layer 116, 118 and the sealing element 161 in the injection mold 192 prevent the gas diffusion layer 116, 118 from deforming under the cavity pressure or injection pressure that occurs during the introduction of the injection molding material into the cavity 196 of the injection mold 192.

This ensures that the areas of the cavity 196 lying outside the deformation limiting elements 184 are completely filled with the injection molding material. The risk of mechanical damage to the connection area 202 of the sealing element 161, in particular the formation of cracks, is thereby reduced.

In addition, damage to the gas diffusion layer 116, 118 due to bending stress due to deformation of the gas diffusion layer 116, 118 is avoided. 8, which shows a partial plan view of the finished assembly 206 of gas diffusion layer 116, 118 and sealing element 161 removed from the injection mold 192, the connection region 202 of the sealing element 161 is in the cavity 196 due to the presence of the deformation limiting elements 184 of the injection mold 192 is provided on an inner edge 222 thereof with recesses 182, which are arranged at the points at which the deformation limiting elements 184 were arranged while the gas diffusion layer 116, 118 was inserted into the injection mold 192.

As can be seen from Fig. 8, it can be provided, for example, that the deformation limiting elements 184 have a circular section-shaped, in particular semicircular, cross section - taken perpendicular to the thickness direction 200 of the gas diffusion layer 116, 118.

Stabilization areas 222 are arranged between the recesses 182 in the connection area 202 of the sealing element 161, in which the sealing element 161 has a greater material thickness than in the area of the recesses 182, so that the stabilization areas 222 ensure a stable mechanical connection of the sealing element 161 to the gas diffusion layer 116, 118 care for.

The position of the outer edge 216 of the gas diffusion layer 116, 118 is indicated in FIG. 8 by the dash-double-dotted line 216.

The position of the tip of the sealing lip 212 of the sealing element 161 is indicated in FIG. 8 by the broken line 224.

In a special variant of the electrochemical device 100 described above, it is further provided that the sealing arrangement 150 has a plurality of recesses 182 in the area of the connecting channel 128 is provided, which are spaced apart from one another along the circumferential direction 152 of the sealing arrangement 150 and are formed on the sealing projection 172, which projects in the area of the connecting channel 128 from the base body 174 of the sealing element 161 in a projection direction 176 facing away from the medium channel 122.

The sealing projection forms a passivation layer made of an elastomeric material, which is preferably molded onto a gas diffusion layer 116, 118 together with at least one sealing lip 212 of the sealing arrangement 150.

The elastomer material is injected onto the gas diffusion layer 116, 118 in a cavity 196 of an injection molding tool 192, as shown schematically in FIG. 9.

The injection molding tool 192 comprises a plurality of deformation limiting elements 184, which are spaced apart from one another along the circumferential direction 152 of the gas diffusion layer 116, 118, are spaced from the push-off edge 198 of the injection molding tool 192 and the gas diffusion layer 116, 118 even before the injection molding material is introduced into the cavity 196 of the injection molding tool 19 2 touch.

10 shows a partial plan view of an assembly 206 produced by means of the injection molding tool 192 from FIG. 9.

The connection area 202 of the sealing element 161 of this assembly 206 is provided with recesses 182, which are arranged outwards from the inner edge 155 of the connection area 202 and are spaced apart from one another in the circumferential direction 152 of the gas diffusion layer 116, 118. 10, the deformation limiting elements 184 in this embodiment have, for example, a circular cross section - taken perpendicular to the thickness direction 200 of the gas diffusion layer 116, 118 - so that the recesses 182 in the connection area 202 also have a circular cross section.

In this embodiment, the deformation limiting elements 184 are arranged between the outer edge 216 of the gas diffusion layer 116, 118 and the push-off edge 198 of the injection molding tool 192, so that in the finished assembly 206 in the area of the sealing projection 172 the outer edge 216 of the gas diffusion layer 116, 118 - along the thickness direction 200 the gas diffusion layer 116, 118 - does not intersect the recesses 182 in the connection area 202 of the sealing element 161.

Regardless of whether the sealing element 161 is provided with one or more recesses 182 in the area of the at least one sealing projection 172 or in at least one area outside of a sealing projection 172, the sealing element 161 can also be used in an injection molding tool 192 of the type shown in FIG Gas diffusion layer 116, 118 are sprayed on.

The push-off tool part 190 and the support tool part 194 each have a push-off projection 188, with a section 226 of the gas diffusion layer 116, 118 being clamped and pressed between the two push-off projections 188.

The porous material of the gas diffusion layer 116, 118 is pressed to such an extent that the elastomer material introduced into the cavity 196 of the injection molding tool 192 does not penetrate the area of the gas diffusion layer lying between the pressing projections 188 or only to a very small extent, so that the area of the gas diffusion layer lying between the pressing projections 188 surrounded central area 228 the gas diffusion layer 116, 118, i.e. the part of the gas diffusion layer 116, 118 used in the electrochemical device 100 for supplying cathode gas or anode gas to the membrane-electrode arrangement 114, is penetrated only minimally.

The push-off projections 188 of the injection molding tool 192 from FIG trained to each other.

The use of such push-off projections 188 can result in damage to the component pressed between the push-off projections 188, which can directly or indirectly cause damage to the electrochemical cell in which the gas diffusion layer 116, 118 is installed, and thus cause failure of the entire fuel cell stack.

By designing at least one of the pressing projections 188 with a geometry that deviates from the usual rectangular geometry, as shown in FIG. 12, the load on the components pressed between the pressing projections 188 in the contact area with the pressing projections 188 is reduced.

This can be achieved by at least one of the pressing projections 188, preferably both pressing projections 188, each having at least one rounded edge, a convexly curved contact surface 232 and/or at least one bevel. The total width W of each push-off projection 188, that is to say its extent perpendicular to the stacking direction 110 and perpendicular to the circumferential direction 152 of the gas diffusion layer 116, 118, is preferably a multiple of the pore size of the gas diffusion layer 116, 118 and is particularly preferably more than 0.5 mm, for example more than 1 mm.

The height h of the push-off projection 188 of the push-off tool part 190 and the height h 'of the push-off projection 188 of the support tool part 194 of the injection molding tool 192, that is, their extent along the thickness direction 200 of the gas diffusion layer 116, 118 and / or the distance by which the respective push-off projection 188 penetrates into the porous material of the gas diffusion layer 116, 118 when the gas diffusion layer 116, 118 is pressed, can be essentially the same size or differ from one another.

If the gas diffusion layer 116, 118 is designed asymmetrically, for example because it has a microporous layer (MPL) on one side or is provided on one side with a catalyst layer, a catalyst layer and a membrane or with a complete membrane-electrode arrangement 114 is, it makes sense to also design the pressing projections 188, between which such an asymmetrical gas diffusion layer 116, 118 is pressed, asymmetrically, as shown in FIG. 14 (in the embodiments according to FIGS. 14 and 15, the sealing element 161 includes a second one Sealing lip 212 ', which can be opposite the first sealing lip 212).

The injection molding tool 192 is advantageously designed so that that tool part of the injection molding tool 192 which is on the side of the gas diffusion layer 116, 118 that has a microporous layer or on the one side with a catalyst layer, with a catalyst layer and a membrane or with a complete membrane electrodes -Arrangement 114 provided side of the gas diffusion layer 116, 118, extends less far into the material of the gas diffusion layer 116, 118 than the other tool part of the injection molding tool 192. For example, it can be provided that on one side of the gas diffusion layer 116, 118 the push-off projection 188 of the relevant tool part of the injection molding tool 192 is completely eliminated, as shown in FIG. 13.

This is preferably the side of the gas diffusion layer 116, 118 which is provided with a microporous layer (MPL), with a catalyst layer, with a catalyst layer and a membrane or with a complete membrane-electrode arrangement 114.

In the injection molding tool 192 shown in Fig. 15, the pressing projections 188 are designed such that their contact surfaces 232 are not continuously convexly curved, but have a central section 234 which is aligned essentially parallel to the main surfaces 218 of the gas diffusion layer 116, 118, and two inclined sections 236, which are inclined at an angle a or a 'with respect to the main surfaces 218 of the gas diffusion layer 116, 118.

It is preferably provided that the angle of inclination a or a' is smaller than 60°, particularly preferably smaller than 45°.

If one of the sides of the gas diffusion layer 116, 118, for example a side which has a microporous layer (MPL), a catalyst layer, a membrane or a complete membrane-electrode arrangement 114, is particularly sensitive to handle, then it can be advantageous , if this side of the gas diffusion layer 116, 118 is at least partially in contact with a contact element 238 of the injection molding tool 192, which is elastically deformable, as shown in Fig. 16, during the introduction of the injection molding material into the cavity 196 of the injection molding tool 192.

Such a contact element 238 can, for example, include a coating 240 made of an elastomeric material. Such a coating 240 made of an elastomeric material can be produced on one of the tool parts of the injection molding tool 192, for example, by means of a pattern printing process, preferably a screen printing process or a pad printing process.

Alternatively or in addition to this, it can be provided that the injection molding tool 192 includes a contact element 238, which is manufactured separately from the push-off tool part 190 and separately from the support tool part 194 of the injection molding tool 192 and, after its production, on the push-off tool part 190 or on the Support tool part 194 has been arranged, as shown in Fig. 17.

The contact element 238 can be arranged in particular in a groove 242 on the relevant tool part 190 or 194.

Furthermore, the contact element 238 can have one or more support lips 244.

Claims

Claims Electrochemical device, comprising a stack (104) of several electrochemical units (106) successive along a stacking direction (110), each of which has an electrochemically active membrane-electrode arrangement (114), a bipolar plate (112) and a sealing arrangement (150 ) include at least one medium channel (122), which extends along the stacking direction (110) through several of the electrochemical units (106), at least one flow field (124) through which a medium from the medium channel (122) transversely to the stacking direction (110) can flow from the medium channel (122) to another medium channel, and at least one connecting channel (128), through which the flow field (124) and the medium channel (122) are in fluid communication with one another, the connecting channel (128) having an edge web (142), through which the medium from the medium channel (122) flows during operation of the electrochemical device (100), a coolant channel (148) separated from the interior (144) of the edge web (142) by a joining line (134). a coolant flows through it during operation of the electrochemical device (100), wherein the flow field (124) comprises an edge channel (140) which is arranged between the edge web (142) and the coolant channel (148) and from which during operation of the electrochemical device Medium flows through from the medium channel (122), and wherein the sealing arrangement (150) extends along the circumferential direction (152) of the flow field (124) around the flow field (124) and has an inner edge (155) which has a cathode side electrochemically active surface (160) or an anode-side electrochemically active surface (158) of the membrane-electrode arrangement (114), characterized in that the inner edge (155) of the sealing arrangement (150) lies on the side of the edge web (142) facing away from the medium channel (122). Electrochemical device according to claim 1, characterized in that the inner edge (155) of the sealing arrangement (150) lies on the side of the coolant channel (148) facing the medium channel (122). Electrochemical device according to one of claims 1 or 2, characterized in that the inner edge (155) of the sealing arrangement (150) lies in the area of the edge channel (140). Electrochemical device according to one of claims 1 to 3, characterized in that the connecting channel (128) is formed between two bipolar plate layers (130, 132) which are fixed to one another at the joining line (134). Electrochemical device according to one of claims 1 to 4, characterized in that the inner edge (155) of the sealing arrangement (150) lies on the side of the joining line (134) facing away from the medium channel (122). Electrochemical device according to one of claims 1 to 5, characterized in that the inner edge (155) of the sealing arrangement (150) is formed on a sealing element (161) of the sealing arrangement (150), which is cohesively bonded to a gas diffusion layer (118) of the relevant electrochemical Unit (106) is connected. Electrochemical device according to claim 6, characterized in that the sealing element (161) is formed from an elastomeric material. Electrochemical device according to claim 7, characterized in that the elastomer material of the sealing element (161) penetrates a connection area of the gas diffusion layer (118). Electrochemical device according to one of claims 6 to 8, characterized in that the sealing element (161) comprises a sealing projection (172) which, in the area of the connecting channel (128), extends from a base body (174) of the sealing element (161) into one of the medium channel (122) projects away from the projection direction (176). Electrochemical device according to claim 9, characterized in that the sealing projection (172) extends along the circumferential direction (152) of the base body (174) of the sealing element (161) only over a part of the circumference of the base body (174) of the sealing element (161). Electrochemical device according to one of claims 9 or 10, characterized in that the extent (B) of the sealing projection (172) perpendicular to its circumferential direction (152) is greater than the extent (b) of the edge web (142) perpendicular to the circumferential direction (152 ). Electrochemical device according to one of claims 1 to 11, characterized in that an extension of the sealing arrangement (150) perpendicular to its circumferential direction (152) in the area of the connecting channel (128) is greater than in at least one area outside the area of the connecting channel (128) . Electrochemical device according to claim 12, characterized in that the sealing arrangement (150) is provided in the area of the connecting channel (128) with a plurality of recesses (182), which are spaced apart from one another along the circumferential direction (152) of the sealing arrangement (150) and are formed on a sealing projection (172) which, in the area of the connecting channel (128), extends from a base body (174) of the sealing element (161) into one of the medium channel (122 ) projecting direction (176) facing away from it. Electrochemical device according to one of claims 12 or 13, characterized in that the sealing arrangement (150) is provided in the at least one area outside the connecting channel (128) with a plurality of recesses (182) which are along the circumferential direction (152) of the sealing arrangement (150 ) are spaced apart from one another and are arranged on the inner edge (155) of the sealing arrangement (150), and/or that the inner edge (155) of the sealing arrangement (150) is wave-shaped in the at least one area outside the connecting channel (128). Electrochemical device according to one of claims 1 to 14, characterized in that the medium which flows through the connecting channel (128) during operation of the electrochemical device (100) is an anode gas or a cathode gas of the electrochemical device (100). Electrochemical device according to one of claims 1 to 15, characterized in that the inner edge (155) of the sealing arrangement (150) borders a cathode-side electrochemically active surface (160) of the membrane-electrode arrangement (114). Electrochemical device according to one of claims 1 to 16, characterized in that an outer edge (178) of an electrochemically active surface (160) on the cathode side of the membrane-electrode arrangement (114) is opposite an outer edge (180) of an electrochemically active surface on the anode side Surface (158) of the membrane-electrode arrangement (114) is offset inwards. Method for producing a sealing element (161) on a gas diffusion layer (116, 118) of an electrochemical unit (106), the method comprising the following:

arranging an injection molding tool (192) on the gas diffusion layer (116, 118);

Introducing injection molding material into a cavity (196) of the injection molding tool (192); wherein the sealing element (161) comprises a sealing projection (172) which projects from a base body (174) of the sealing element (161) in a projection direction (176) pointing into an interior of the sealing element (161), the sealing projection (172). along the circumferential direction (152) of the base body (174) of the sealing element (161) extends only over a part of the circumference of the base body (174) of the sealing element (161), characterized in that the injection molding tool (192) comprises at least one deformation limiting element (184). , which limits or prevents deformation of the gas diffusion layer (116, 118) during the introduction of the injection molding material into the cavity (196), the injection molding tool (192) comprising at least one push-off tool part (190) which has a push-off projection (188) for pressing the gas diffusion layer (116, 118) and wherein the at least one deformation limiting element (184) is spaced from the push-off projection (188) of the push-off tool part (190) during the introduction of the injection molding material into the cavity (196) of the injection molding tool (192). Method according to claim 18, characterized in that the pressing projection (188) of the pressing tool part (190) has at least one rounding and/or at least one bevel. Method according to claim 18 or 19, characterized in that one side of the gas diffusion layer (116, 118) is provided with at least one catalyst layer and this side of the gas diffusion layer (116, 118) during the introduction of the injection molding material into the cavity (196) of the injection molding tool ( 192) is at least partially in contact with a contact element (238) of the injection molding tool (192), which comprises an elastomeric material.