CN113921849A

CN113921849A - Bipolar plate with welded connections

Info

Publication number: CN113921849A
Application number: CN202110776880.1A
Authority: CN
Inventors: C·昆茨; A·斯派德尔; T·斯托尔; B·格伦瓦尔德; W·库恩
Original assignee: Reinz Dichtungs GmbH
Current assignee: Reinz Dichtungs GmbH
Priority date: 2020-07-09
Filing date: 2021-07-09
Publication date: 2022-01-11
Also published as: DE102021207304A1; DE202020103982U1

Abstract

The invention relates to a bipolar plate (2) for an electrochemical system, comprising: the sealing element comprises two separate plates (2a, 2b) which are welded together, metal, at least one sealing element (30, 32 ') which is self-closing and which serves to seal the region of the bipolar plate (2), at least one weld seam (34, 36) which extends at least in some regions along the sealing element (30, 32 ') and is self-closing, and at least one weld connection (38, 40) which is arranged on the same side of the sealing element (30, 32 ') as the weld seam (34, 36), wherein the weld connection (38, 40) extends only in sections along the weld seam (34, 36).

Description

Bipolar plate with welded connections

Technical Field

The present invention relates to a bipolar plate for an electrochemical system and an electrochemical system having a plurality of stacked bipolar plates. The electrochemical system may be, for example, a fuel cell system, an electrochemical compressor, a redox flow battery, or an electrolysis device.

Background

Known electrochemical systems generally comprise stacks of electrochemical cells, which are in each case separated from one another by bipolar plates. Such bipolar plates may be used, for example, for indirect electrical contact of the electrodes of a single electrochemical cell (e.g., a fuel cell) and/or for electrical connection of adjacent cells (series connection of cells). Bipolar plates are typically formed from two separate plates joined together. The individual plates of the bipolar plate can be joined together in a material-fit (mass-bonded), for example by means of one or more welded connections, in particular by means of one or more laser-welded connections.

The bipolar plates or the individual plates can each have a structure or form a structure which is designed, for example, for supplying one or more media and/or conveying reaction products to the electrochemical cells delimited by adjacent bipolar plates. The medium may be a fuel (e.g., hydrogen or methanol) or a reactant gas (e.g., air or oxygen). Furthermore, the bipolar plate or the individual plate structures can be used for conducting the cooling medium through the bipolar plate, in particular through a cavity enclosed by the individual plate(s) of the bipolar plate. In addition, the bipolar plates can be designed and constructed to transfer waste heat generated during the conversion of electrical or chemical energy in the electrochemical cell and to seal various media or cooling channels from one another and/or from the environment.

In addition, the bipolar plates usually have a plurality of channel openings in each case. The media and/or reaction products can be conducted through the channel openings into the electrochemical cells delimited by the stacked adjacent bipolar plates or into cavities formed by the individual plates of the bipolar plates, or out of the cells or from the cavities. Electrochemical cells also typically include one or more Membrane Electrode Assemblies (MEAs) accordingly. The MEA can have one or more gas diffusion layers, which are usually oriented toward the bipolar plates and are formed, for example, from metal or carbon felt.

The seal between the bipolar plate and the mea is usually carried out outside the electrochemically active area and usually comprises at least one port seal arranged around the channel openings and (one) an outer seal, which may be designed as a bead structure.

In general, the flange stiffness of the flange structure is not constant due to the shape and course of the adjacent relief elements along the main extension direction of the flange structure. Furthermore, different course shapes of the collar, for example straight or curved sections, result in different collar stiffnesses in the sections of different course shapes. The above-mentioned influencing factors may locally increase the elasticity of the chimes, which in turn may have a negative influence on the original compression of the respective chimes in their respective sections.

There is a risk here that: the medium will flow through the bead structure in a region of less compression or the working medium flows into the inner space of the bipolar plate and the coolant flows into the outer space of the bipolar plate. In this case, on the one hand, the medium is lost for the operation of the electrochemical system. On the other hand, there is a risk that: the coolant reaches the region of the working medium and there damages the MEA.

Due to the large number of bipolar plates or individual plate plates in the stack, small differences in compression and rebound of the bead structures in individual bipolar plates or individual metal individual plates along their course can lead to relatively large differences in rebound of the bead structures connected in series, so that small differences in individual plates have a significant effect on the tightness of the entire stack.

Disclosure of Invention

The task of the present invention is therefore to propose a bipolar plate which allows a more uniform compression of the same bipolar plates in the stack, without the space required for the seal being much greater than that required for the seals of the prior art. Furthermore, an electrochemical system with a plurality of bipolar plates stacked is to be specified.

This object is achieved by a bipolar plate and an electrochemical system according to the independent claims. Further developments are the subject matter of the dependent claims, also part of the following description.

Thus, a bipolar plate for an electrochemical system is proposed, comprising:

two separate plates of metal (two metal single plates) welded together,

at least one self-closing sealing element for sealing an area of the bipolar plate,

at least one weld seam which extends at least regionally (partially) along the sealing element and is self-closing,

at least one weld connection, which is arranged on the same side of the sealing element as the weld seam, wherein the weld connection extends only in sections (partially) along the weld seam.

By providing an additional welded connection, the sealing element can be locally reinforced, whereby a more even distribution of the force on the sealing element can be achieved. This may better ensure that the individual plates contact each other in the area between the sealing element and the self-closing weld. The welded connection also prevents the individual plates from bowing (bulging) or deforming outwards from the plane of the plate. Overall, the compressive force around the sealing element can be homogenized, whereby undesired local deformations of the bipolar plate or of the individual plates can be reduced. Thereby, even the necessary compressive forces in the stack can be reduced, which has a positive effect on the lifetime of the bipolar plate and the electrochemical system. Since the available space in this region is usually limited, the welded connection does not extend completely along the weld seam, but only partially (in sections).

The welding connection may have various shapes. In some embodiments, the welded connection is point-shaped, linear or curved. For example, the welded connection can be composed of sections of the above-described shape. Here, the linear shape shall include a straight line, but also includes a polygonal line. Curved may mean that at least one curved section is provided. It is also possible that a plurality of arcuate sections are joined together to form a wave-shaped section. The welded connection can have two end sections which are spaced apart from one another and are therefore not connected to one another. In another alternative embodiment, the welded connection is self-closing (self-closing). In this case, the welded connection may be, for example, circular, oval or elliptical. However, other shapes are also contemplated.

It can be provided that the welded connection has a plurality of welding sections that are separate, in particular spaced apart from one another. For example, the welded connection has a double interlocking seam (Steppnaht) which comprises linear or curved welding sections arranged on one another, in particular spaced apart relative to one another.

The self-closing weld seam may be formed by a single, continuous welded connection. Alternatively, the self-closing weld seam can also have at least two weld seam sections which comprise overlapping ends to form a closed weld seam.

For example, a welded connection is arranged where there is sufficient space. For example, the weld connection may be arranged at least in sections (at least partially), for example, between the sealing element and the weld seam. Alternatively or additionally, the weld seam may be arranged between the sealing element and a section of the weld connection. For example, the sealing element is located inside or outside the area enclosed by the self-closing weld. The welded connection may be located inside or outside the area enclosed by the self-closing weld.

Typically, the welded connections, welds and/or sealing elements are spaced apart from each other. Preferably, the distance between the welded connection and the sealing element is at least 0.3mm, preferably 0.6 mm. Preferably, the distance between the weld seam and the sealing element is at least 0.7mm, preferably 1.0 mm. In other words, it can be provided that the welded connection and the weld seam do not contact the sealing element.

In contrast, the weld seam and the welded connection can be arbitrarily adjoined to one another. In a further embodiment, the welded connection intersects the weld seam. Alternatively, provision can also be made for the weld seam and the welded connection to be spaced apart from one another. The length of the self-closing weld seam is typically at least two times, preferably at least ten times, greater than the length of each individual welded connection.

It can be provided that the welded connections, the sealing elements and/or the weld seam extend partially (partially) parallel and/or concentrically to one another. Provision can be made for the welded connection and the weld seam to form a double weld seam in regions. In this case, the welded connection and the weld seam can have the same course (trajectory/extension) or the same shape. In some embodiments, the weld seam and/or the sealing element have a wavy course. In this case, the wave-like course can have at least two wave periods with a convex section and a concave section which merge into one another at the turning point. At least one section of the welded connection may face a female section of the weld seam and/or a female section of the sealing element. However, it is also possible for at least one section of the welded connection to face the convex section of the weld seam and/or the convex section of the sealing element.

In some embodiments, the individual plates are welded together by laser welding. In this case, the welded connection and/or the weld seam can be a laser welded connection or a laser weld seam.

The sealing element may comprise a bead in at least one individual plate, preferably in both individual plates, which bead protrudes from the plate plane of the respective individual plate. The bead structure can be designed as an embossing structure, which is produced, for example, by means of deep drawing, embossing (embossing) and/or hydroforming. For example, the chime may have a chime top and at least one chime side flap adjacent to the chime top. For example, the chime has a chime top, two chime flanks and at least in sections (partial) two chime feet. Alternatively, the raised edge structure may have a curved raised edge roof that transitions directly into the likewise arcuate side flaps.

The bipolar plate or the metal separate plate can have an embossed structure, which is produced, for example, by means of deep drawing, embossing and/or hydroforming. These further relief structures may have, in addition to the sealing elements already mentioned above, structures for guiding the medium along the structure of the individual plates of metal, such as flow fields and/or channel structures. The sealing element may surround the relief structure, for example in a self-closing manner. The sealing element may, for example, have a peripheral flange that surrounds the flow field and seals it from the surrounding environment of the metal layer. In some embodiments, the sealing element may surround at least one passage opening for gas or liquid, which is self-closing, formed on a separate plate. For example, the sealing structure may have a port bead that seals the passage opening for the media.

An electrochemical system is also proposed. The electrochemical system comprises a plurality of stacked bipolar plates of the aforementioned type.

In particular, the bipolar plate can be produced by the method described below.

First, a separate plate of a first metal is provided. The first separate plate is shaped to form a (self-) closing sealing element. Thereafter or simultaneously, a separate plate of the second metal is provided. Alternatively, a (self-) closing sealing element can also be formed here. The two separate plates are then placed together and welded together to form the bipolar plate. When the individual plates are brought together, the sealing elements are usually positioned relative to one another such that they project from the respective plate plane of the individual plates on opposite sides of the bipolar plate. In the case of welding, at least one weld seam can first be provided which extends at least in some regions (partially) along the sealing element and is (self-) closed. It is thereby possible to produce a welded connection which is arranged on the same side of the sealing element as the weld seam, wherein the welded connection extends only in sections (partially) along the weld seam. Alternatively, the individual plates can also be connected first by means of a welded connection and then by means of a weld seam. Alternatively, the weld seam and the welded connection may be provided in one production step. Thus, the weld seam and the weld connection can be produced at least partially simultaneously or alternately.

It should be noted here that the features of the production method described can be combined with the features of the bipolar plate described above and vice versa.

Drawings

Embodiments of bipolar plates and electrochemical systems are shown in the drawings and explained in detail in light of the following description. The figures show:

fig. 1 schematically illustrates, in perspective view, an electrochemical system having a plurality of individual plates or bipolar plates arranged in a stack;

fig. 2 shows schematically in a perspective view two bipolar plates of the system according to fig. 1, between which a Membrane Electrode Assembly (MEA) is arranged;

figure 3A schematically shows a cross section through a subregion of a bipolar plate used in the system according to figure 1;

figure 3B schematically shows a cross section through a sub-region of a bipolar plate used in the system according to figure 1;

figure 3C schematically shows a cross section through a sub-region of a bipolar plate used in the system according to figure 1;

figure 4 schematically shows a top view of a subregion of a bipolar plate with a different welded connection;

figure 5 schematically shows a top view of a subregion of another bipolar plate with a different welded connection;

figure 6 schematically shows a top view of a subregion of another bipolar plate with a different welded connection;

figure 7 schematically shows a top view of a subregion of another bipolar plate with a different welded connection;

figure 8 schematically shows a top view of a subregion of another bipolar plate with a different welded connection;

figure 9 schematically shows a top view of a subregion of another bipolar plate with a different welded connection;

figure 10 schematically shows a top view of a subregion of another bipolar plate with a different welded connection;

figure 11 schematically shows a top view of a subregion of another bipolar plate with a different welded connection;

figure 12 schematically shows a top view of a subregion of another bipolar plate with a different welded connection;

figure 13 schematically shows a top view of a subregion of another bipolar plate with a different welded connection; and

figure 14 schematically shows a top view of a subregion of another bipolar plate with a different welded connection.

Detailed Description

Here and in the following, features which are repeated in different figures are correspondingly denoted by the same or similar reference numerals.

Fig. 1 shows an electrochemical system 1, the electrochemical system 1 having a plurality of identical metallic bipolar plates 2, which are arranged in a stack 6 and stacked in the z-direction 7. The bipolar plates 2 of the stack 6 are sandwiched between two

end plates

3, 4. The z-direction 7 is also referred to as "stacking direction". In this example, the system 1 relates to a fuel cell stack. Every two adjacent bipolar plates 2 in the stack thus contain an electrochemical cell between them, which electrochemical cell is used, for example, for converting chemical energy into electrical energy. To form the electrochemical cells of the system 1, a Membrane Electrode Assembly (MEA) is disposed between each of the stacked adjacent bipolar plates 2 (see, e.g., fig. 2). Each MEA typically includes at least one membrane, e.g., an electrolyte membrane. Further, a Gas Diffusion Layer (GDL) may be disposed on one or both surfaces of the MEA.

In alternative embodiments, system 1 may also be designed as an electrolysis device, an electrochemical compressor or a redox flow battery. Bipolar plates may also be used in these electrochemical systems. The structure of these bipolar plates may correspond to the structure of the bipolar plate 2 explained in detail here, even in the case of electrolyzers, in the case of electrochemical compressors or in the case of redox flow batteries, the media fed to the bipolar plates or through the bipolar plates may be different from the media used for the fuel cell system accordingly.

The z-axis 7, together with the x-axis 8 and the y-axis 9, encloses a right-handed cartesian coordinate system. Each bipolar plate 2 accordingly defines a plate plane, wherein the plate planes of the individual plates are accordingly oriented parallel to the x-y plane and thus perpendicular to the stacking direction or z axis 7. The end plate 4 has a plurality of media connections 5 through which media can be fed into the system 1 and through which media can be discharged from the system 1. The medium which can be fed to the system 1 and which can be discharged from the system 1 can for example comprise a fuel such as molecular hydrogen or methanol, a reaction gas such as air or oxygen, a reaction product such as water vapour or depleted fuel, or a coolant such as water and/or ethanol.

Fig. 2 shows, in perspective, two adjacent bipolar plates 2, 2 'of an electrochemical system of the type of the system 1 shown in fig. 1 and a Membrane Electrode Assembly (MEA)10 arranged between these adjacent bipolar plates 2, 2', as is known in the art, wherein the MEA 10 in fig. 2 is largely covered by the bipolar plate 2 facing the viewer. The bipolar plate 2 consists of two

individual plates

2a, 2b which are joined together in a material-fit (mass-bonded) manner (see also fig. 3, for example), wherein in fig. 2 only the first individual plate 2a facing the observer is visible in each case, which covers the second individual plate 2 b. The

individual plates

2a, 2b may each be made of a metal plate, for example of a stainless steel plate. The

separate plates

2a, 2b may for example be welded together, for example by laser welding.

The

individual plates

2a, 2b have channel openings aligned with one another, which form the channel openings 11a-c of the bipolar plate 2. When stacking together a plurality of bipolar plates of the type of bipolar plate 2, the channel openings 11a-c form guides which extend through the stack 6 in the stacking direction 7 (see fig. 1). Typically, each of the guides formed by the channel openings 11a-c is in fluid connection with a respective one of the ports 5 in the end plate 4 of the system 1. The guide formed by the passage opening 11a can be used, for example, for introducing coolant into the stack or for leading coolant out of the stack. In contrast to this, the guide formed by the

passage openings

11b, 11c can be designed and configured for supplying fuel and reactant gases to the electrochemical cells of the fuel cell stack 6 of the system 1 and for extracting reaction products from the stack. The medium-conducting passage openings 11a-11c are designed substantially parallel to the plane of the plates.

In order to seal the channel openings 11a-c with respect to the interior space of the stack 6 and with respect to the surroundings, the first individual plate 2a accordingly has a sealing arrangement (sealing structure) in the configuration of sealing beads (sealing beads) 12a-c, which are respectively arranged around the channel openings 11a-c and respectively completely surround the channel openings 11 a-c. The second individual plate 2b has corresponding sealing beads at the back side of the bipolar plate 2 facing away from the viewer of fig. 2 for sealing the channel openings 11a-c (not shown).

In the electrochemically active region 18, the first individual plate 2a has, at its front side facing the viewer of fig. 2, a flow field 17 with a structure for guiding the reaction medium along the front side of the individual plate 2 a. These structures are given in fig. 2 by webs and channels extending between and bounded by the webs. At the front side of the bipolar plate 2 facing the viewer of fig. 2, the first individual plate 2a also comprises a distribution or collection area 20, respectively. The distribution or collection area 20 comprises a structure which is arranged such that the medium which is introduced into the distribution or collection area 20 and which originates from a first of the two passage openings 11b is distributed over the active area 18 and/or the medium which flows out of the active area 18 into the second passage opening 11b is collected or collected. In fig. 2, the distribution structure of the distribution or collection area 20 is also given by the webs and the passageways extending between and bounded by the webs. In general, the

elements

17, 18, 20 can be understood as an embossed structure (embossing structure) of the conductive medium.

The sealing beads 12a to 12c have through-openings 13a to 13c, which are embodied here as local elevations of the beads, wherein the through-openings 13a are embodied both on the underside of the upper separate plate 2a and on the upper side of the lower separate plate 2b, while the through-openings 13b are formed in the upper separate plate 2a and the through-openings 13c are formed in the lower separate plate 2 b. For example, the through-openings 13a allow the coolant to pass between the passage openings 12a and the distribution area, so that the coolant reaches or is guided away from the distribution area between the individual plates. Furthermore, the through portions 13b allow the passage of hydrogen between the passage openings 12b and the distribution area on the upper side of the separate plate 2a located above, these through portions 13b being characterized by perforations facing the distribution area and extending obliquely with respect to the plate plane. Thereby, for example, the hydrogen gas flows from the passage opening 12b to the distribution area on the upper side of the individual plate 2a located at the upper portion through the through portion 13b, or flows in the opposite direction. For example, the through-openings 13c allow air to pass between the passage openings 12a and the distribution area, so that the air reaches or is guided away from the distribution area on the underside of the individual plate 2b located below. The associated (associated) perforation is not visible here.

The first individual plate 2a also comprises a further sealing structure in the configuration of the peripheral flange 12d, which surrounds the flow field 17 of the active region 18, the distribution or collection region 20 and the

channel openings

11b, 11c and seals (isolates) them from the channel openings 11a, i.e. from the coolant circuit, and from the surroundings of the system 1. The second individual plate 2b comprises a corresponding peripheral flange, respectively. The structure of the active area region 18, the distribution structure of the distribution or collection area 20 and the sealing beads 12a-d are each integrally formed with the separate plate 2a and are molded into the separate plate 2a, for example in a embossing process, a hydroforming process or a deep drawing process. This also applies to the corresponding dispensing structure and sealing bead of the second separate plate 2 b. Outside the area enclosed by the peripheral flange 12d, there is a main, unstructured peripheral area 22 in each

individual plate

2a, 2 b.

The two channel openings 11b or the guides formed by the channel openings 11b, which pass through the plate stack of the system 1, are in flow connection with one another by means of the through-openings 13b in the sealing bead 12b, by means of the distribution structure of the distribution or collection region 20 and by means of the flow field 17 in the active region 18 of the first individual plate 2a facing the viewer of fig. 2, respectively. In a similar manner, the through openings 11c through the plate stack of the system 1 or the guides formed by the through openings 11c are in fluid connection with each other by means of the corresponding collar through-portions, by means of the corresponding distribution structures and by means of the corresponding flow fields on the outer side of the second individual plate 2b facing away from the viewer of fig. 2, respectively. In contrast to this, the passage openings 11a, or the guides formed by the passage openings 11a, through the plate stack of the system 1 are in each case fluidically connected to one another via a cavity 19 enclosed or surrounded by the

individual plates

2a, 2 b. This cavity 19 correspondingly serves for conducting a coolant through the bipolar plate 2, in particular for cooling the electrochemically active region 18 of the bipolar plate 2.

Fig. 3A-3C show schematically a section through a part of a bipolar plate 2 for a system according to fig. 1 with

separate plates

2a, 2b, respectively. Here, the flange structure is generally indicated by reference numerals 12, 12', like for example one of the flange structures 12a-12 d. As already described in connection with fig. 2, the two

individual plates

2a, 2b each comprise a bead structure 12, 12' which are arranged opposite one another and form an embossment which projects from the plate plane in the Z direction. The chimes 12, 12 'generally each comprise a chime top, two chime side flanks adjoining the chime top, and two chime feet adjoining the chime side flanks, wherein the chime feet of the chimes 12, 12' contact each other and form a contact surface in this region. Alternatively, the respective bead structure 12, 12' can have a curved (curved) bead apex, which merges directly into a likewise curved flank. In the stack 6, adjacent bipolar plates 2, 2 'press the bead structures 12, 12' together. Specifically, the raised edge tops of adjacent bipolar plates 2, 2' in the stack 6 face each other, with at least a portion of the MEA 10 typically sandwiched therebetween.

In fig. 3A it can be seen that the

individual panels

2a, 2b diverge from each other with increasing lateral distance from the foot of the collar. This has a negative effect on the compression of the chimes 12, 12' and may lead to an unsealed position of the stack 6, which may lead to undesired fluid flow. The present invention is conceived to solve or mitigate this problem. Fig. 3B and 3C show that the weld seams 34, 36 or welded (connected) portions adjacent to the sealing element can reduce (fig. 3B) such splitting (splaying), particularly in the case of joining the weld seams 34, 36 and welded (connected) portions 38, 40 (fig. 3C) substantially completely preventing such splitting (splaying). Thereby, the stiffness of the adjacent sealing elements is increased or can be adjusted in a targeted manner by applying additional weld connections in a targeted manner. In particular, by means of the invention, the different welded connections and the sealing element or the bead structure are joined to one another, so that a more uniform compressive force on the sealing element or the bead structure is achieved.

Fig. 4-14 show detailed views of a bipolar plate 2 according to various embodiments of the present invention. It should be noted here that the bipolar plates 2 shown in fig. 4 to 14 can be used in the system according to fig. 1 and in the structure according to fig. 2 in general. Fig. 4 to 14 each show a partial region of the bipolar plate 2, which has at least one self-

closing sealing element

30, 32 for sealing off a region of the bipolar plate 2. The sealing

elements

30, 32 are preferably embodied as

bead structures

12, 12' or 12a-d of the type described above.

Furthermore, a weld 34 is provided, which extends along the sealing element 30 in sections (partially) and is self-closing. The weld 34 surrounds the active region 18 and all the channel openings 11a-c at the fluid inlet side and at the fluid outlet side of the bipolar plate 2. Furthermore, the sealing element 30, the active area 18 and the passage openings 11a-c are located in the area enclosed by the self-closing weld 34. Since fig. 4 to 14 each show only one subregion of the bipolar plate 2, only a portion of the weld seam 34 or sealing element 30 is shown here. The weld 34 may be comprised of a single, uninterrupted weld segment. However, it is expedient for the weld seam 34 to be produced if the weld seam 34 comprises a plurality of weld seam sections, the end sections of which are connected to one another and intersect at an intersection point 35.

Additionally or alternatively, a further self-closing weld 36 may be provided, which extends partially (partially) along the sealing element 32 and also extends around one of the passage openings 11 b-c. In the embodiment of fig. 4-14, the weld 36 extends around the passage opening 11 b. In particular, the passage opening 11b and the sealing element 32 are located entirely within the area enclosed by the self-closing weld 36. As in the case of the weld seam 34, the weld seam 36 can likewise consist of a single, uninterrupted weld seam section. In practice, the weld 36 is typically made up of a plurality of weld segments that intersect at an intersection point 37.

In order to reinforce the sealing

elements

30, 32 in certain regions (regionally), welded

connections

38, 40 are provided, which are arranged on the same side of the sealing

elements

30, 32 as the welding seams 34, 36. The

weld connections

38, 40 extend only in sections (partially) along the weld seams 34, 36. The welded

connections

38, 40 are preferably arranged where the

respective sealing element

30, 32 should be reinforced and there is sufficient space. As can be seen from the figures, the

weld connections

38, 40 may be arranged, for example, between the sealing

elements

30, 32 and the weld seams 34, 36. Alternatively, the weld seams 34, 36 may be arranged between the

weld connections

38, 40 and the sealing

elements

30, 32. The

weld connections

38, 40 may be located within or outside the area encompassed by the self-closing

welds

34, 36.

The welded

connections

38, 40 may have different shapes. For example, a welded

connection

38, 40 having a straight section and an arcuate section is shown in fig. 4-14. For example, the welded

connection

38, 40 may have two end sections which are not connected to one another. Alternatively, the welded

connections

38, 40 may be self-closing, such as circular, oval or elliptical (see circular welded connections of fig. 4, 5 and 14).

Although the sealing element 32 surrounding the passage opening 11b has a substantially circular course (trajectory) in the exemplary embodiment of fig. 4 to 13, it is shown, for example, in fig. 4, 5, 6, 9, 11 and 14: the sealing element 32' surrounding the passage opening 11a can have a more complex course with straight, curved and/or wavy sections, which also applies to the passage opening 11b in fig. 14. Furthermore, the sealing element 30 can also have different sections, which are shaped differently. The course (trajectory) of the sealing element 30 can have at least two wave-shaped sections, see the peripheral flange 12d of fig. 2. Likewise for the sealing element 32', the wavy section can be seen in the cross sections shown in fig. 4, 5, 6, 9, 11 and 14, as can also be seen for the sealing element 32 of fig. 14. The sealing element 30, 32' can thus have a wave-shaped course (track/extension) in sections, wherein the wave-shaped course has a plurality of wave periods with a convex section and a concave section, which respectively merge into one another at the point of inflection. The shape of the

welds

34, 36 is generally dependent upon the shape of the respective sealing element 30, 32'. In the embodiments of fig. 5, 6, 9, 11 and 14, the weld seam 34 runs essentially parallel to the sealing element 30 and therefore also has the same path (course). In contrast, in fig. 4, 8, 10, 12, 13, the weld seam 34 has a substantially straight course (path/extension), wherein the sealing element 30 has an undulating course. In general, at least the main directions of extension of the sealing element 30 and the weld seam 34 may extend at least in sections (partially) in parallel. The weld seam 34 and the weld connection 38 can run parallel to one another and form a double weld seam in this region.

In particular, for reasons of space, it is generally preferred to arrange the weld connection 38 adjacent to the concave section of the weld seam 34 and/or the concave section of the sealing element 30, as shown in fig. 4, 5, 8, 10, 13 and 14. Functionally, however, it may also be preferred to arrange the weld connection 38 adjacent to the male section of the weld 34 and/or the male section of the sealing element 30, as shown in fig. 6.

Fig. 7 features a sealing element 30 and a weld 34 which are both wave-shaped in sections (partially), but are out of phase. In the illustrated embodiment, the phase difference is 180 °. A weld connection (spot weld) 38 is arranged at a position where the weld 34 and the sealing element 30 are separated from each other. Here, the weld 38 therefore also faces in particular the concave section of the weld 34 and the concave section of the sealing element 30.

A plurality of welded connections 38 arranged at regular intervals relative to each other may form a double-line interlocking seam (Steppnaht) 42. Such a double interlocking seam 42 is provided in the embodiment of fig. 6 and 11, for example.

In general, the

weld connections

38, 40, the

welds

34, 36 and the sealing elements 30, 32', respectively, are spaced apart from each other and therefore do not touch each other, see fig. 4-7, 9, 11, 13 and 14. However, it may also be provided that the welded connection 38 and the weld seam 34 intersect. Such a situation is shown in fig. 8, 10, 12.

In order to further strengthen the sealing element 30, an additional weld connection 39 is shown in fig. 9, wherein the weld seam 34 and the weld connection 39 are arranged on different sides of the sealing element 30. The respective solder connections 39 are arranged at regular intervals. Some welded connections 39 are arranged between the sealing element 30 and the weld seam 36.

An alternative weld connection 39 is shown in fig. 14, wherein the weld seam 36 and the weld connection 39 are arranged on different sides of the sealing element 30. The embodiment of fig. 14 also comprises a further optional weld seam 44, which weld seam 44 is arranged in sections around the passage opening 11a, while the weld seam 36 continues in the direction of the passage opening 11c around the passage opening 11b and the weld seam, not shown, there around the passage opening 11 c. In the embodiment of fig. 14, a weld section 45 is present, which is arranged between the

passage openings

11a and 11b, in particular between the sealing elements 32, 32' of the

passage openings

11a, 11 b. The welded portion 45 is a constituent part of the weld seam 36.

In the following it will be described how the bipolar plate 2 is manufactured.

First, two

separate plates

2a, 2b of metal are manufactured. To this end, the sealing

elements

30, 32 and the other relief structures shown in fig. 2 are first molded into the individual layers of metal by embossing, deep drawing or hydroforming. Various surface treatment steps may be carried out thereafter, for example, which are known in the art and are not described further here.

After production, the

individual plates

2a, 2b are placed on top of each other and welded together, thereby forming the bipolar plate 2. The weld seams 34, 36 are preferably applied first, after which the welded

connections

38, 40 are provided. It should be noted here that the weld seams 34, 36 and the

weld connections

38, 40 can also be produced in one step, i.e. simultaneously or partly simultaneously.

Preferably, the weld seams 34, 36 and the

weld connections

38, 39, 40 are produced by laser welding. However, alternative welding methods are also conceivable. After the welding step, the bonded bipolar plate 2 may be fed to a further processing step for subsequent insertion into the stack 6 of the electrochemical system 1.

List of reference numerals:

1 electrochemical system

2 Bipolar plate

2' bipolar plate

2a separate plate

2b individual plates

3 end plate

4 end plate

5 medium interface

6 Stacking

7 z direction

8 x direction

9 y direction

10 membrane electrode assembly

11a-d channel opening

12 convex edge structure

12' convex edge structure

12a-d chime structure

13a-c penetration part

17 flow field

18 electrochemically active area

19 cavity

20 distribution and/or collection area

22 unstructured outer zone

30 sealing element

32 sealing element

32' sealing element

34 weld seam

35 intersection point

36 welding seam

37 intersection point

38 welded connection

39 welded connection

40 welded connection

42 double-line interlocking seam

44 weld seam

45 welding the segment.

Claims

1. A bipolar plate (2) for an electrochemical system, comprising:

two separate plates (2a, 2b) of metal welded together,

-at least one self-closing sealing element (30, 32') for sealing an area of the bipolar plate (2),

at least one weld seam (34, 36) which extends at least in some regions along the sealing element (30, 32') and is self-closing,

-at least one weld connection (38, 40) arranged on the same side of the sealing element (30, 32') as the weld seam (34, 36), wherein the weld connection (38, 40) extends only in sections along the weld seam (34, 36).

2. A bipolar plate (2) as claimed in claim 1, wherein the welded connection (38, 40) is punctiform, linear or curved or is composed of sections of the aforementioned shapes.

3. The bipolar plate (2) according to one of the preceding claims, wherein the welded connection (38, 40) has a plurality of welded segments which are separate, in particular spaced apart from one another.

4. A bipolar plate (2) as claimed in claims 2 and 3, characterised in that the welded connection (38, 40) has:

-a double-line interlocking seam (42) comprising linear or arc-shaped welding sections aligned to each other, in particular spaced apart with respect to each other.

5. The bipolar plate (2) according to one of the preceding claims, wherein the sealing element (30, 32') is located within the region enclosed by the self-closing weld seam (34, 36).

6. The bipolar plate (2) according to one of the preceding claims, wherein the welded connection (38, 40) is located inside or outside the region enclosed by the self-closing weld seam (34, 36).

7. The bipolar plate (2) according to one of the preceding claims, wherein the welded connections (38, 40), the weld seams (34, 36) and/or the sealing elements (30, 32') are spaced apart relative to one another.

8. The bipolar plate (2) according to one of the preceding claims, wherein the welded connection (38, 40) and the weld seam (34, 36) intersect.

9. The bipolar plate (2) according to one of the preceding claims, wherein the welded connection (38, 40) and the weld seam (34, 36) form a double weld seam in regions.

10. The bipolar plate (2) according to one of the preceding claims, wherein the weld seam (34, 36) and/or the sealing element (30, 32') has a wavy course.

11. The bipolar plate (2) according to claim 10, characterised in that the wavy course has at least two wave periods with a convex section and a concave section, which transition into one another at a turning point, wherein the weld connection (38, 40) faces the concave section of the weld seam (34, 36) and/or the concave section of the sealing element (30, 32').

12. The bipolar plate (2) according to one of claims 10 and 11, characterized in that the wavy course has at least two wave periods with a convex section and a concave section, which transition into one another at a turning point, wherein the weld connection (38, 40) faces the convex section of the weld seam (34, 36) and/or the convex section of the sealing element (30, 32').

13. The bipolar plate (2) according to one of the preceding claims, wherein the individual plates (2a, 2b) are welded together by means of laser welding.

14. The bipolar plate (2) according to one of the preceding claims, characterised in that the sealing element (30, 32') has a bead structure in at least one of the individual plates (2a, 2b), preferably in both individual plates (2a, 2b), which bead structure projects out of the plate plane of the respective individual plate (2a, 2 b).

15. An electrochemical system (1) comprising a plurality of stacked bipolar plates (2) according to any one of the preceding claims.