WO2024079180A2

WO2024079180A2 - Electrochemical device

Info

Publication number: WO2024079180A2
Application number: PCT/EP2023/078174
Authority: WO
Inventors: Jürgen KRAFT; Manuel Morcos
Original assignee: Ekpo Fuel Cell Technologies Gmbh
Priority date: 2022-10-13
Filing date: 2023-10-11
Publication date: 2024-04-18
Also published as: WO2024079180A3; DE102022126790A1

Abstract

The invention relates to an electrochemical device, comprising a stack of multiple electrochemical units which follow one another along a stacking direction and each of which comprises an electrochemically active membrane-electrode assembly, a bipolar plate, and a seal assembly, wherein the seal assembly comprises an outermost sealing line which lies closest to the outer edge of the bipolar plate, and each electrochemical unit comprises an elastomer body which is in contact with a first bipolar plate of the electrochemical unit and a second bipolar plate of an adjacent electrochemical unit. The aim of the invention is to provide such an electrochemical device in which an undesired deviation of the bipolar plate in the stack of electrochemical units from the flat position thereof in the stack is reduced or prevented. This is achieved in that at least one of the bipolar plates, said bipolar plate being in contact with the elastomer body, has at least one compression element, along which the elastomer body is supplied with a compressive force in the operating state of the electrochemical device. The at least one compression element is arranged between the outermost sealing line of the seal assembly and the outer edge of the respective bipolar plate.

Description

Electrochemical device

The present invention relates to an electrochemical device comprising a stack of a plurality of electrochemical units arranged successively along a stacking direction, wherein the electrochemical units each comprise an electrochemically active membrane electrode arrangement, a bipolar plate and a sealing arrangement, wherein the sealing arrangement comprises an outermost sealing line which is closest to an outer edge of the bipolar plate, and wherein each electrochemical unit comprises an elastomer body which is in contact with a first bipolar plate of the electrochemical unit and with a second bipolar plate of an adjacent electrochemical unit.

In particular, when the bipolar plates of the electrochemical units of such an electrochemical device are manufactured from thin metallic foils in a punching and embossing process, stresses arise in the punched and formed bipolar plate, which lead to deformation, in particular deflection, of the unloaded bipolar plate.

The occurrence of these mechanical stresses in the bipolar plate is often associated with the fact that the punched and formed bipolar plates can switch between two stable states when a corresponding mechanical load occurs, a phenomenon colloquially referred to as "clicking frog".

If a bipolar plate is manufactured by welding two bipolar plate layers, both of which have such mechanical stresses and a corresponding deformation, any cracking frog that may be present is usually even more pronounced, and the Alignment of the bipolar plates, in which the main surfaces of the bipolar plates are aligned perpendicular to the stacking direction of the stack of electrochemical units, required force higher.

The phenomenon described is due to the fact that the deformation of the structures with three-dimensional geometries (webs, channels, full beads, half beads) on the bipolar plate results in mechanical stresses and/or restoring forces remaining in the deformed, in particular embossed, bipolar plate, particularly when the structures with the three-dimensional geometries have intersecting courses. These stresses and/or restoring forces result in deflections of the bipolar plate from its flat position in the stack of electrochemical units.

The undesirable deformation of the bipolar plates results in disadvantages in the assembly process of the electrochemical device, in which bipolar plates and membrane electrode assemblies (MEAs) are stacked on top of each other in alternating sequence.

The components of the stack then come into contact with each other in the bent state and perform a relative movement to each other when the stack is pressed together.

The deformation caused by the "clicking frog" effect is often particularly strong in the outer edge area of the bipolar plates. Since, when the electrochemical units of the stack are clamped, high forces are introduced into the stack along the stack direction in the area of the flow fields, where the gas diffusion layers contact the webs of the bipolar plates, and in the area of the sealing arrangements that surround the flow fields and the medium channels of the electrochemical device that run parallel to the stack direction, and thus at a large distance from the outer edge of the bipolar plates, a deformation of the bipolar plates in their outer edge area can remain even after the electrochemical units of the stack have been pressed together. The relatively small forces required to flatten a single bipolar plate add up in a stack of, for example, several hundred electrochemical units, so that the undesirable deformations of the bipolar plates can persist even in a pressed stack of electrochemical units, which can have a negative impact on the sealing effectiveness of the gasket assemblies and on other aspects of the electrochemical devices that require precise alignment and spacing of the electrochemical units within the stack.

The present invention is based on the object of creating an electrochemical device of the type mentioned at the outset, in which an undesirable deviation of the bipolar plates in the stack of electrochemical units from their flat position in the stack is reduced or avoided.

This object is achieved according to the invention in an electrochemical device having the features of the preamble of claim 1 in that at least one of the bipolar plates with which the elastomer body is in contact has at least one compression element along which the elastomer body is subjected to a compression force in the operating state of the electrochemical device, wherein the at least one compression element is arranged between the outermost sealing line of the sealing arrangement and the outer edge of the respective bipolar plate.

The present invention is based on the concept of introducing a compression force in the region of the outer circumference of the electrochemical units which is relatively small compared to the force introduced via the flow fields of the bipolar plates and is relatively small compared to the force introduced via the sealing lines of the sealing arrangement. This can be achieved, for example, by applying small compression forces specific to the length of an extended linear compression element.

Alternatively or in addition to this, it can also be provided that specifically larger compression forces are introduced via locally limited compression elements, whereby, however, the overall resulting compression force should always still be small compared to the surface pressure force in the electrochemically active region of the electrochemical unit.

The elastomer body preferably forms a soft and elastic component which is locally deformed by the at least one compression element.

Due to the elasticity of the elastomer body, only small total forces occur to reduce or avoid undesirable deformations of the bipolar plate in its outer edge area, so that sufficient pressing force is still available for pressing the electrochemical units in their electrochemically active area.

The elastomer body arranged between a first bipolar plate of an electrochemical unit and a second bipolar plate of an adjacent electrochemical unit preferably has a width (i.e. an extension perpendicular to the stacking direction and perpendicular to the sealing lines of the sealing arrangement) which is greater than the width of the gap remaining between the two bipolar plates in the clamped state of the stack.

A compression element of the first bipolar plate and/or a compression element of the second bipolar plate can be unstructured and/or flat. Alternatively or additionally, a compression element of the first bipolar plate can be designed as a bead, in particular as a full bead.

A compression element of the second bipolar plate can also be designed as a bead, for example as a full bead.

Preferably, the beads of the compression element of the first bipolar plate and the compression element of the second bipolar plate are aligned in the same direction, i.e. the bead crests of these beads are offset in the same direction relative to the bead feet of the beads.

In this case, the upper edges of the bead arranged below the elastomer body and the lower edges of the bead arranged above the elastomer body form compression lines along which the elastomer body is compressed.

The smallest distance (along the stacking direction) between the first bipolar plate and the second bipolar plate is along these compression lines. In the areas adjacent to the compression lines, the distance between the first bipolar plate and the second bipolar plate is preferably greater than the height of the elastomer body (i.e. its extension along the stacking direction).

The elastomer material of the elastomer body can bulge from the compression lines into their vicinity.

The linear compression elements can dig into the elastomer body. The force introduced into the elastomer body along the linear compression elements is overall only small, so that the contact resistance of the electrochemical units is not increased and the sealing effect of the sealing arrangement is not reduced.

The elastomer body preferably forms part of the sealing arrangement and can in particular be formed integrally with one or more sealing elements of the sealing arrangement.

The beads which form the compression elements of the first bipolar plate or the second bipolar plate preferably run around the respective bipolar plate close to its outer edge.

Instead of full beads, these beads can also be designed as half beads.

As an alternative to a compression element that is ring-shaped and runs around the respective bipolar plate, it can also be provided that the compression element is designed to be locally limited.

The compression element of a bipolar plate can also be designed as a cutting edge that digs into the elastomer body.

Locally formed compression elements can, for example, be rotationally symmetrical.

A compression element of a bipolar plate can also be designed as a tab punched out of the bipolar plate and flared out.

The elastic restoring force of the tab, which prevents bending of the tab, can increase the compression force transmitted by the compression element. The elastomer body can form part of the sealing arrangement of an electrochemical unit.

Alternatively or additionally, it can also be provided that the elastomer body is materially connected to at least one of the adjacent bipolar plates.

If the sealing arrangement comprises a frame element made of a material that is hard compared to an elastomer material, the elastomer body can be connected to such a frame element in a form-fitting and/or material-fitting manner.

It is particularly advantageous if, in the assembly process of the stack of electrochemical units, the at least one compression element of the bipolar plate adjacent to the elastomer body comes into engagement with the elastomer body before the sealing arrangement and/or a gas diffusion layer of the electrochemical unit comes into contact with a next bipolar plate of an adjacent electrochemical unit of the stack stacked thereon. In this way, the bipolar plate of the electrochemical unit in question can be brought into the flat or planar shape before the other functional elements of the electrochemical unit are aligned with one another.

This can be achieved, for example, by the elastomer body having a thickening or a lip that protrudes along the stacking direction beyond the sealing lips of the sealing arrangement, so that the thickening or lip structure of the elastomer body comes into contact with the next bipolar plate stacked on the elastomer body during the assembly process before this further bipolar plate comes into contact with the sealing lips of the sealing structure. At the start of the assembly process, a first bipolar plate, which is stacked - possibly with a seal arranged in between - on an end plate or another edge element that delimits the stack of electrochemical units, should already be supported in such a way that a flat alignment of the first bipolar plate can be enforced by the force introduction of the components stacked on this first bipolar plate.

This is achieved, for example, by the end plate having the same geometry as the bipolar plate in the areas that determine the introduction of force and by the same sealing arrangement being used between the end plate and the first bipolar plate as between two bipolar plates arranged one after the other along the stacking direction, including the elastomer body, which is compressed by means of the compression elements of the bipolar plates adjacent to the elastomer body. If the sealing arrangement comprising the elastomer body is connected in an electrochemical unit to its membrane electrode arrangement and/or to one of its gas diffusion layers, such a membrane electrode arrangement or gas diffusion layer should also be arranged on the end plate in a corresponding manner, whereby the catalyst of the catalyst-coated membrane can be omitted if necessary or the catalyst-coated membrane can be replaced entirely by an electrochemically inactive film in order to save costs.

In a preferred embodiment of the invention, it is provided that both bipolar plates with which the elastomer body is in contact each have a compression element along which the elastomer body is subjected to a compression force in the operating state of the electrochemical device.

Preferably, at least one of the compression elements is in contact with the elastomer body along at least one linear compression point. The linear contact point can be designed to be self-contained.

Alternatively, it can be provided that the linear contact point extends from a beginning to an end without being self-contained.

In a preferred embodiment of the invention, it is provided that at least one of the compression elements is designed as a stiffening bead.

For example, it can be provided that at least one of the compression elements is designed as a full bead.

Alternatively or additionally, it can be provided that at least one of the compression elements is designed as a half-bead.

Preferably, the compression elements of the first bipolar plate and the second bipolar plate are both designed as full bead or both as half bead.

A first linear compression point at which the elastomer body is in contact with the first bipolar plate can be located along the stacking direction above or below a second linear compression point at which the elastomer body is in contact with the second bipolar plate.

Alternatively or additionally, it can be provided that a first linear compression point, at which the elastomer body is in contact with the first bipolar plate, has a first distance from an outer edge of the first bipolar plate, which is smaller or larger than a second distance that a second linear compression point, at which the elastomer body is in contact with the second bipolar plate, has from the outer edge of the second bipolar plate. In a preferred embodiment of the invention, it is provided that the elastomer body projects outward beyond the outer edge of the first bipolar plate and/or beyond the outer edge of the second bipolar plate.

The elastomer body is preferably formed in one piece.

The elastomer body is preferably formed entirely from an elastomer material.

The elastomer body can be formed from an elastomer material in particular by an injection molding process.

In a preferred embodiment of the invention, it is provided that the elastomer body is formed integrally with a sealing element of the sealing arrangement.

In order to avoid bending of the elastomer body, it is advantageous if the elastomer body comprises a support base with which the elastomer body is supported on the first bipolar plate or on the second bipolar plate.

In order to avoid an increase in the contact resistance of the electrochemical units and/or a reduction in the sealing effect of the sealing arrangements of the electrochemical units, it is advantageous if, in the operating state of the electrochemical device, the sum of the compression forces exerted by one of the bipolar plates on the at least one compression element on the elastomer body is smaller than the sum of the contact forces exerted by a flow field of the bipolar plate on the membrane electrode arrangement with which the bipolar plate is in contact and/or is smaller than the sum of the sealing forces exerted by the bipolar plate at the sealing lines on the sealing arrangement with which the bipolar plate is in contact.

Preferably, in the operating state of the electrochemical device, the sum of the compression forces exerted by one of the bipolar plates on the at least one compression element on the elastomer body is less than a third, in particular less than a fifth, particularly preferably less than a tenth, of the sum of the contact forces exerted by a flow field of the bipolar plate on the membrane electrode arrangement with which the bipolar plate is in contact, and/or less than a third, in particular less than a fifth, particularly preferably less than a tenth, of the sum of the sealing forces exerted by the bipolar plate at the sealing lines on the sealing arrangement with which the bipolar plate is in contact.

The electrochemical device according to the invention can be designed in particular as a fuel cell device or as an electrolyzer.

The electrochemical device can in particular be designed as a polymer electrolyte membrane (PEM) fuel cell device.

Further features and advantages of the invention are the subject of the following description and the drawings of embodiments.

The drawings show:

Fig. 1 is a plan view from above along the stacking direction of a fuel cell stack of a fuel cell device onto a part the fuel cell stack, which comprises two fuel cell units arranged consecutively in the stacking direction of the fuel cell stack and a bipolar plate of a third fuel cell unit arranged above the two fuel cell units;

Fig. 2 is a partial longitudinal section through the part of the fuel cell stack from Fig. 1, along the line 2-2 in Fig. 1, wherein each fuel cell unit comprises an elastomer body which is in contact with a first bipolar plate of the fuel cell unit and with a second bipolar plate of an adjacent fuel cell unit, wherein the bipolar plates each have a compression element along which the elastomer body is subjected to a compression force in the operating state of the electrochemical device and which is designed as a full bead;

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

Fig. 4 is an enlarged view of area II of Fig. 2;

Fig. 5 is a plan view from above along the stacking direction of a fuel cell stack of a fuel cell device of a part of the fuel cell stack according to a second embodiment of the fuel cell device, wherein the part of the fuel cell stack comprises two fuel cell units arranged one after the other in the stacking direction of the fuel cell stack and a bipolar plate of a third fuel cell unit lying above the two fuel cell units;

Fig. 6 is a partial longitudinal section through the part of the fuel cell stack from Fig. 5, along the line 6 - 6 in Fig. 5, wherein each fuel cell unit comprises an elastomer body, which is in contact with a first bipolar plate of the fuel cell unit and with a second bipolar plate of an adjacent fuel cell unit, wherein each of the bipolar plates has a compression element along which the elastomer body is subjected to a compression force in the operating state of the fuel cell device and which is designed as a half-bead;

Fig. 7 is an enlarged view of area III of Fig. 6; and

Fig. 8 shows a partial longitudinal section through a third embodiment of an electrochemical device, which differs from the first embodiment shown in Figs. 1 to 4 in that the sealing arrangement comprises a frame element made of a material that is harder than an elastomer material, in particular a plastic material, wherein the elastomer body is connected to the frame element in a form-fitting and/or material-fitting manner and the elastomer body has local thickenings.

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

An electrochemical device, shown in detail in Figs. 1 and 2 and 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, wherein the stack 104 comprises a plurality of electrochemical units 106 arranged one after the other in a stacking direction 110 and a (not shown) clamping device for applying a clamping force to the electrochemical units 106 directed along the stacking direction 110 (see in particular Fig. 2).

As best seen from the cross-sectional view in Fig. 2, 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, wherein the first gas diffusion layer 116 is arranged, for example, on the cathode side and the second gas diffusion layer 118 is arranged, for example, on the anode side.

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

As can best be seen from Fig. 1, the bipolar plate 112 has a plurality of medium passage openings 120, through each of 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 arranged one after the other in the stack 104 and the gaps lying between the medium passage openings 120 in the stacking direction 110 together 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 respective fluid medium can be discharged 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 from the first medium channel 122 transversely, preferably substantially perpendicularly, to the stacking direction 110 through the respective flow field 124 to the second medium channel 122.

For example, Fig. 1 shows an anode gas supply channel 126, an anode gas discharge channel 128, a cathode gas supply channel 130, a cathode gas discharge channel 132, a coolant supply channel 134 and a coolant discharge channel 136.

Each flow field 124 is connected to a medium feed channel and to a medium discharge channel via a connecting channel. The flow fields 124 for anode gas and for cathode gas are each delimited at their outer edge by an edge web 138, which lies flat against an adjacent membrane electrode arrangement 114.

In the embodiment shown in the drawing, each bipolar plate 112 comprises a first bipolar plate layer 140 and a second bipolar plate layer 142, which are secured to one another in a fluid-tight manner along connecting lines 144 which run perpendicular to the plane of the drawing in Fig. 2, preferably in a material-locking manner, in particular by welding, for example by laser welding.

An undesirable leakage of the fluid media from the flow fields 124 of the electrochemical device 100 is prevented in each electrochemical unit 106 by a sealing arrangement 146 which extends around the flow fields 124 along the circumferential direction 148 of the flow fields 124. The sealing arrangement 146 preferably comprises two sealing elements 150, wherein a first sealing element 152 is preferably fixed to the cathode-side first gas diffusion layer 116 and a second sealing element 154 is preferably fixed to the anode-side second gas diffusion layer 118 of the membrane electrode arrangement 114.

For example, it can be provided that the sealing elements 152 and 154 are injection-molded or cast onto the respectively associated gas diffusion layer 116 or 118.

The first sealing element 152 preferably has one or more sealing lips 156, with which the first sealing element 152 rests fluid-tight against the first bipolar plate layer 140 of a first adjacent bipolar plate 112 in order to form a sealing line 158 which extends around a flow field 124 of the electrochemical device 100, so that escape of medium from the flow field 124 into the environment or into one of the medium channels 122, which are assigned to other media than the relevant flow field 124, is prevented (see Fig. 3).

The second sealing element 154 preferably has one or more sealing lips 160, with which the second sealing element 154 rests fluid-tight against the second bipolar plate layer 142 of a second bipolar plate 112' of an adjacent electrochemical unit 106' in order to form a sealing line 162 which extends around a flow field 124 of the electrochemical device 100, so that escape of medium from the relevant flow field 124 into the environment or into medium channels 122 which are associated with other media than the relevant flow field 124 is prevented. One of the sealing lines 158 and 162, which is located furthest outward, i.e. closest to the outer edge 164 of the bipolar plates 112, as viewed from the center of the flow fields 124 of the electrochemical device, forms an outermost sealing line 166 of the sealing arrangement 146.

If several of the sealing lines 158 and 162 lie exactly one above the other along the stacking direction 110, a sealing arrangement 146 can also have several outermost sealing lines 166 lying one above the other along the stacking direction 110.

In Fig. 2, the sealing lips 156, 160 are shown in their compressed state, which they assume when the electrochemical units 106 of the stack 104 have been clamped against each other.

In this pressed state, the tips of the sealing lips 156, 160 are flattened. The sealing lines 158, 162 of the sealing arrangement 146 then run approximately where the tips of the sealing lips 156, 160 were in the unpressed state of the electrochemical device 100.

As can be seen from Fig. 2, each electrochemical unit 106 of the stack 104 further comprises an elastomer body 168 which is in contact with a first bipolar plate 112 of the same electrochemical unit 106 and with a second bipolar plate 112' of an adjacent electrochemical unit 106'.

An outer edge 169 of the elastomer body 168 facing away from the membrane electrode arrangement 114 of the electrochemical unit 106 is preferably offset outwardly relative to the outer edges 164 of the bipolar plates 112, 112' adjacent to the elastomer body 168. Each of the bipolar plates 112, 112' with which the elastomer body 168 is in contact has a compression element 170 along which the elastomer body 168 is subjected to a compression force in the operating state of the electrochemical device 100.

The first bipolar plate 112 comprises a first compression element 170a, which is formed as a stiffening bead 172 in the first bipolar plate layer 140 of the bipolar plate 112 (see Fig. 4).

In this embodiment, the stiffening bead 172 is designed as a full bead 174 which has an inner first bead edge 176 facing the flow field 124, an inner second bead edge 178 offset outwards from the inner first bead edge 176 in an offset direction 180 oriented perpendicular to the stacking direction 110 and along the stacking direction 110 towards the second bipolar plate layer 142 of the bipolar plate 112, an outer second bead edge 182 offset outwards from the inner second bead edge 178 in the offset direction 180 and an outer first bead edge 184 offset outwards from the outer second bead edge 182 in the offset direction 180 and away from the second bipolar plate layer 142 of the bipolar plate 112 along the stacking direction 110.

The inner first bead edge 176, the inner second bead edge 178, the outer second bead edge 182 and the outer first bead edge 184 extend along the circumferential direction 148 around the flow fields 124 of the respective electrochemical unit 106 and are preferably self-contained.

The inner first bead edge 176 and the inner second bead edge 178 delimit an inner bead flank 186 of the stiffening bead 172.

The outer second bead edge 182 and the outer first bead edge 184 delimit an outer bead flank 188 of the stiffening bead 172. The inner second bead edge 178 and the outer second bead edge 182 delimit a bead crest 190 of the stiffening bead 172.

As can be seen from Fig. 4, the inner first bead edge 176 and the outer first bead edge 184 of the stiffening bead 172 each form a linear compression point 192, along which the compression element 170 of the first bipolar plate 112 designed as a stiffening bead 172 is in contact with the elastomer body 168.

The linear compression points 192 formed by the inner first bead edge 176 and the outer first bead edge 184 are preferably designed to be closed in themselves.

The second compression element 170b, with which the second bipolar plate 112' is in contact with the elastomer body 168, is formed as a stiffening bead 172' in the second bipolar plate layer 142 of the second bipolar plate 112'.

In the first embodiment shown in Figs. 1 and 4, this second compression element 170b is also designed as a full bead 174'.

The stiffening bead 172' has an inner first bead edge 194, an inner second bead edge 196 offset from the inner first bead edge 194 in the offset direction 180 outward and along the stacking direction 110 away from the first bipolar plate layer 140 of the second bipolar plate 112', an outer second bead edge 198 offset from the inner second bead edge 196 in the offset direction 180 outward and an outer first bead edge 200 offset from the outer second bead edge 198 in the offset direction 180 outward and along the stacking direction 110 toward the first bipolar plate layer 140 of the second bipolar plate 112' (see Fig. 4). The inner first bead edge 194, the inner second bead edge 196, the outer second bead edge 198 and the outer second bead edge 200 each extend along the circumferential direction 148 around the flow fields 124 of the respective electrochemical unit 106 and are preferably designed to be closed in themselves.

The inner first bead edge 194 and the inner second bead edge 196 delimit an inner bead flank 202 of the stiffening bead 172'.

The outer second bead edge 198 and the outer first bead edge 200 delimit an outer bead flank 206 of the stiffening bead 172'.

The inner second bead edge 196 and the outer second bead edge 198 delimit a bead crest 204 of the stiffening bead 172'.

As can be seen from Fig. 4, the inner second bead edge 196 and the outer second bead edge 198 of the stiffening bead 172' in the second bipolar plate layer 142 of the second bipolar plate 112' each form a linear compression point 192, along which the compression element 170b of the second bipolar plate 112' is in contact with the elastomer body 168.

The linear compression points 192 formed by the inner second bead edge 196 and by the outer second bead edge 198 are preferably designed to be closed in themselves.

The first compression element 170a of the first bipolar plate 112 and the second compression element 170b of the second bipolar plate 112' are each arranged between the outermost sealing line 166 of the sealing arrangement 146 and the outer edge 164 of the first bipolar plate 112 and the second bipolar plate 112', respectively. In particular, the linear compression points 192 of the compression elements 170a and 170b are arranged between the outermost sealing line 166 of the sealing arrangement 146 and the outer edge 164 of the bipolar plates 112 and 112', respectively, when these elements are projected onto a plane oriented perpendicular to the stacking direction 110.

As can be seen from Fig. 4, the inner first bead edge 176, at which the elastomer body 168 is in contact with the first bipolar plate 112, has a distance from the outer edge 164 of the first bipolar plate 112 that is greater than the distance that the outer second bead edge 198, at which the elastomer body 168 is in contact with the second bipolar plate 112', has from the outer edge 164 of the second bipolar plate 112'.

Furthermore, the distance of the inner first bead edge 176, at which the elastomer body is in contact with the first bipolar plate 112, from the outer edge 164 of the first bipolar plate 134 is smaller than the distance of the inner second bead edge 196, at which the elastomer body 168 is in contact with the second bipolar plate 112', from the outer edge 164 of the second bipolar plate 112'.

The distance of the outer first bead edge 184, at which the elastomer body 168 is in contact with the first bipolar plate 112, from the outer edge 164 of the first bipolar plate 112 is greater than the distance of the outer second bead edge 198, at which the elastomer body 168 is in contact with the second bipolar plate 112', from the outer edge 164 of the second bipolar plate 112'.

Furthermore, the distance of the outer first bead edge 184, at which the elastomer body 168 is in contact with the first bipolar plate 112, from the outer edge 164 of the first bipolar plate 112 is smaller than the distance the inner second bead edge 196, at which the elastomer body 168 is in contact with the second bipolar plate 112', from the outer edge 164 of the second bipolar plate 112'.

The linear compression points 192 of the first compression element 170a, along which the elastomer body 168 is subjected to a compression force by the first bipolar plate 112 in the operating state of the electrochemical device 100, are thus located - when projected onto a plane perpendicular to the stacking direction 110 - between the linear compression points 192' of the second compression element 170b, along which the elastomer body 168 is subjected to a compression force by the second bipolar plate 112' in the operating state of the electrochemical device 100.

The bead crest 190 of the stiffening bead 172 of the first compression element 170a is narrower than the bead crest 204 of the stiffening bead 172' of the second compression element 170b.

Furthermore, the stiffening bead 172 of the first compression element 170a is received between the inner bead flank 202 and the outer bead flank 206 of the stiffening bead 172' of the second compression element 170b.

The bead crest 190 of the stiffening bead 172 of the first compression element 170a preferably rests, particularly preferably flatly, on the bead crest 204 of the stiffening bead 172' of the second compression element 170b.

As a result, the stiffening beads 172 and 172' of the two compression elements 170a and 170b support each other, thereby increasing the mechanical stability of the compression elements 170a and 170b. In the operating state of the electrochemical device 100, the sum of the compression forces exerted by one of the bipolar plates 112 or 112' on the elastomer body 168 is smaller than the sum of the contact forces exerted by a flow field 124 of the bipolar plate 112 or 112' on the membrane electrode assembly 114 with which the bipolar plate 112 or 112' is in contact.

Furthermore, in the operating state of the electrochemical device 100, the sum of the compression forces exerted by one of the bipolar plates 112 or 112' on the elastomer body 168 is smaller than the sum of the sealing forces exerted by the bipolar plate 112 or 112' at the sealing lines 158 or 162 on the sealing arrangement 146 with which the bipolar plate 112 or 112' is in contact.

The elastomer body 168 is preferably formed in one piece.

Furthermore, the elastomer body 168 is preferably formed integrally with a sealing element 150 of the sealing arrangement 146.

In the embodiment of an electrochemical device 100 shown in the drawing, it is provided that the elastomer body 168 is formed integrally with the anode-side second sealing element 154 of the sealing arrangement 146.

In principle, however, it could also be provided that the elastomer body 168 is formed integrally with the cathode-side first sealing element 152 of the sealing arrangement 146.

The elastomer body 168 further comprises a support base 208, with which the elastomer body 168 is supported on one of the bipolar plates 112 or 112'. In the embodiment shown in the drawing, the elastomer body 168 is supported by the support base 208 on the second bipolar plate 112'.

In the region of the support base 208, the elastomer body 168 has its greatest height, that is, its greatest extension along the stacking direction 110 of the stack 104 of electrochemical units 106.

The height of the elastomer body 168 in the region of the support base 208 corresponds approximately to the minimum tolerable distance between the bipolar plates 112 and 112' following one another along the stacking direction.

The presence of the support base 208 prevents the elastomer body 168 from bending towards the bipolar plate 112' on which the support base 208 is supported.

The presence of the compression elements 170a and 170b on the bipolar plates 112, 112' of the stack 104 of electrochemical units 106 ensures that both the bipolar plates 112, 112' and the surfaces of the sealing arrangements 146 interacting with them lie flat in the operational stack 104 of electrochemical units 106 and, in particular, all surfaces which are intended to be aligned perpendicular to the stacking direction 110 assume this alignment orthogonal to the stacking direction 110.

Because the compression forces exerted on the elastomer body 168 by means of the compression elements 170a, 170b are smaller than the sealing forces exerted on the sealing lines 158, 162 of the sealing arrangement 146, a reduction in the sealing effect of the sealing arrangement 146 is avoided. Because the compression forces exerted on the elastomer body 168 by means of the compression elements 170a, 170b are smaller than the forces with which the membrane electrode arrangement 114 is acted upon by the flow fields 124 of the bipolar plates 112, 112', and are preferably smaller than a third, in particular smaller than a fifth, particularly preferably smaller than a tenth, of the forces with which the membrane electrode arrangement 114 is acted upon by the flow fields 124 of the bipolar plates 112, 112', an increase in the contact resistance in the region of the flow fields 124 of the bipolar plates 112, 112' is avoided.

A second embodiment of an electrochemical device 100 shown in Figs. 5 to 7 differs from the first embodiment shown in Figs. 1 to 4 in that the stiffening beads 172, 172' of the compression elements 170a, 170b of the first bipolar plate 112 and the second bipolar plate 112', respectively, are not designed as full beads 174, but instead as half beads 210.

The half-bead 210 of the first compression element 170a, with which the first bipolar plate 112 is in contact with the elastomer body 168, is formed in the first bipolar plate layer 140 of the first bipolar plate 112 and has an inner bead line 212 facing the flow field 124 of the bipolar plate 112 and an outer bead line 214 offset from the inner bead line 212 in the offset direction 180 outward and along the stacking direction 110 away from the second bipolar plate layer 142 of the first bipolar plate 112.

The inner bead line 212 and the outer bead line 214 of the half-bead 210 extend along the circumferential direction 148 around the flow fields 124 of the bipolar plates 112, 112' and are preferably designed to be closed in themselves. The inner bead line 212 and the outer bead line 214 of the half-bead 210 delimit a bead flank 215 of the half-bead 210.

The outer bead line 214 of the half-bead 210 of the first bipolar plate 112 forms a linear compression point 192 at which the first bipolar plate 112 is in contact with the elastomer body 168.

At the compression point 192, a deformation of the elastomer body 168 occurs, which is not shown in the drawing for reasons of simplification.

The half-bead 210' of the second compression element 170b is formed in the second bipolar plate layer 142 of the second bipolar plate 112' and has an inner bead line 216 facing the flow field 124 of the second bipolar plate 112' and an outer bead line 218 offset from the inner bead line 216 in the offset direction 180 outward and along the stacking direction 110 toward the first bipolar plate layer 140 of the second bipolar plate 112'.

The inner bead line 216 and the outer bead line 218 of the half-bead 210 extend along the circumferential direction 148 around the flow fields 124 of the bipolar plates 112, 112' and are preferably self-contained.

The inner bead line 216 and the outer bead line 218 delimit a bead flank 220 of the half-bead 210'.

The inner bead line 216 of the half-bead 210' forms a linear compression point 192', along which the second bipolar plate 112' exerts a compression effect on the elastomer body 168. This linear compression point 192' is formed in a closed ring shape.

As can be seen from Fig. 7, the distance of the outer bead line 214 of the half-bead 210 of the first compression element 170a of the first bipolar plate 112 from the outer edge 164 of the first bipolar plate 112 is greater than the distance of the inner bead line 216 of the half-bead 210' of the second compression element 170b of the second bipolar plate 112' from the outer edge 164 of the second bipolar plate 112'.

In this embodiment, the linear compression point 192 of the first compression element 170a of the first bipolar plate 112 is thus further away from the outer edge 164 of the bipolar plates 112, 112' than the linear compression point 192' of the second compression element 170b of the second bipolar plate 112'.

When using a different flank angle for the half beads 210 and 210' and/or due to manufacturing or stacking tolerances, the linear compression point 192 of the first compression element 170a of the first bipolar plate 112 can also be located the same distance away or less far away from the outer edge of the bipolar plates 112, 112' than the linear compression point 192' of the second compression element 170b of the second bipolar plate 112'.

Furthermore, in the second embodiment of an electrochemical device 100 shown in Figs. 5 to 7, the elastomer body 168 is formed integrally with the cathode-side first sealing element 152 of the sealing arrangement 146.

In this embodiment, the support base 208 of the elastomer body 168 is in contact with the first bipolar plate layer 140 of the first bipolar plate 112. Furthermore, the second embodiment of an electrochemical device 100 shown in Figs. 5 to 7 corresponds in terms of structure, function and method of manufacture to the first embodiment shown in Figs. 1 to 4, to the above description of which reference is made in this respect.

A third embodiment of an electrochemical device 100, shown in detail in Fig. 8, differs from the first embodiment shown in Figs. 1 to 4 in that the sealing arrangement 146 of each electrochemical unit 106 comprises a frame element 222 made of a material that is hard compared to an elastomer material, for example a plastic material, wherein the elastomer body 168 is connected to the frame element 222 in a form-fitting and/or material-fitting manner.

For example, it can be provided that the elastomer body 168 is injection-molded or cast onto the frame element 222.

In particular, it can be provided that the elastomer body 168 has a recess 224 into which a height-reduced region 226 of the frame element 222, that is to say a region of the frame element 222 with a reduced extent compared to the height of a base body 228 of the frame element 222, extends along the stacking direction 110 of the electrochemical device 100.

The elastomer body 168 has a thickening 230, 230' on opposite sides, via which the elastomer body 168 is in contact with the first bipolar plate 112 or with the second bipolar plate 112'. Each of the bipolar plates 112, 122' has a compression element 170 along which the elastomer body 168 is subjected to a compression force in the operating state of the electrochemical device, the compression elements 170 being arranged between the outer edge 164 of the respective bipolar plate 112, 112' on the one hand and the outermost sealing line of the sealing arrangement 146 (not shown in Fig. 8, located to the right of the thickened portions 230, 230') on the other hand.

In this embodiment, the compression elements 170 are unstructured and essentially flat.

Furthermore, the third embodiment of an electrochemical device 100 shown in Fig. 8 corresponds in terms of structure, function and method of manufacture to the first embodiment shown in Figs. 1 to 4, to the above description of which reference is made in this respect.

Claims

Claims Electrochemical device comprising a stack (104) of a plurality of electrochemical units (106) arranged one after the other along a stacking direction (110), each comprising an electrochemically active membrane electrode arrangement (114), a bipolar plate (112) and a sealing arrangement (146), wherein the sealing arrangement (146) comprises an outermost sealing line (166) which is closest to an outer edge (164) of the bipolar plate (112), and wherein each electrochemical unit (106) comprises an elastomer body (168) which is in contact with a first bipolar plate (112) of the electrochemical unit (106) and with a second bipolar plate (112') of an adjacent electrochemical unit (106'), characterized in that at least one of the bipolar plates (112, 112') with which the elastomer body (168) is in contact has at least one compression element (170) along which the elastomer body (168) is subjected to a compression force in the operating state of the electrochemical device (100), wherein the at least one compression element (170) is arranged between the outermost sealing line (166) of the sealing arrangement (146) and the outer edge (164) of the respective bipolar plate (112, 112'). Electrochemical device according to claim 1, characterized in that both bipolar plates (112, 112') with which the elastomer body (168) is in contact each have a compression element (170) along which the elastomer body (168) is subjected to a compression force in the operating state of the electrochemical device (100). Electrochemical device according to one of claims 1 or 2, characterized in that at least one of the compression elements (170) is in contact with the elastomer body (168) along at least one linear compression point (192; 192'). Electrochemical device according to claim 3, characterized in that the linear compression point (192; 192') is designed to be self-contained. Electrochemical device according to one of claims 1 to 3, characterized in that the linear compression point (192; 192') extends from a start to an end. Electrochemical device according to one of claims 1 to 5, characterized in that at least one of the compression elements (170) is designed as a stiffening bead (172; 172'). Electrochemical device according to claim 6, characterized in that at least one of the compression elements (170) is designed as a full bead (174; 174'). Electrochemical device according to one of claims 1 to 7, characterized in that at least one of the compression elements (170) is designed as a half bead (210; 210'). Electrochemical device according to one of claims 1 to 7, characterized in that a first linear compression point (192) at which the elastomer body (168) is connected to the first Bipolar plate (112) is in contact, along the stacking direction (110) above or below a second linear compression point (192') at which the elastomer body (168) is in contact with the second bipolar plate (112'). Electrochemical device according to one of claims 1 to 8, characterized in that a first linear compression point (192) at which the elastomer body (168) is in contact with the first bipolar plate (112) has a first distance from an outer edge (164) of the first bipolar plate (112) which is smaller or larger than a second distance that a second linear compression point (192') at which the elastomer body (168) is in contact with the second bipolar plate (112') has from the outer edge (164) of the second bipolar plate (112'). Electrochemical device according to one of claims 1 to 10, characterized in that the elastomer body (168) projects outward beyond the outer edge (164) of the first bipolar plate (112) and/or beyond the outer edge (164) of the second bipolar plate (112'). Electrochemical device according to one of claims 1 to 11, characterized in that the elastomer body (168) is formed in one piece. Electrochemical device according to one of claims 1 to 12, characterized in that the elastomer body (168) is formed in one piece with a sealing element (150) of the sealing arrangement (146). Electrochemical device according to one of claims 1 to 13, characterized in that the elastomer body (168) comprises a support base (208) with which the elastomer body (168) is supported on the first bipolar plate (112) or on the second bipolar plate (112'). Electrochemical device according to one of claims 1 to 14, characterized in that in the operating state of the electrochemical device (100), the sum of the compression forces exerted by one of the bipolar plates (112, 112') on the at least one compression element (170) on the elastomer body (168) is smaller than the sum of the contact forces exerted by a flow field (124) of the bipolar plate (112, 112') on the membrane electrode arrangement (114) with which the bipolar plate (112, 112') is in contact and/or is smaller than the sum of the sealing forces exerted by the bipolar plate (112, 112') at the sealing lines (158, 162) on the sealing arrangement (146) with which the bipolar plate (112, 112') is in contact.