Separator for electrochemical system and corresponding electrochemical system comprising such separator

Abstract

The invention relates to a separator for an electrochemical system, comprising a first individual plate and a second individual plate connected to the first individual plate, where the two individual plates are in contact with each other in a contact region, where the first individual plate comprises two first channels for a conductive medium, formed in the first individual plate, the first channels travel close to each other and are separated from each other at least in some sections by webs formed between the first channels; wherein the second individual plate comprises a second channel for the conducting medium, the second channel being formed in the second individual plate; and wherein the web formed between the first channels and the second channel formed in the second individual plate are constructed and arranged such that a projection of the second channel perpendicular to a plane of the first individual plate to the first individual plate intersects the web along an intersection region of the web; wherein the webs are lowered in the intersection region of the webs such that the first channels running on both sides of the webs are fluidly connected.

Description

Technical Field

[0001] The present invention relates to a separator for an electrochemical system and an electrochemical system comprising such a separator. Background Art

[0002] Known electrochemical systems, such as fuel cell cell systems or electrochemical compressor systems, redox flow batteries and electrolyzers, usually comprise a plurality of separators arranged in a stack, so that in each case two adjacent separators enclose an electrochemical cell. The separators usually each comprise two separate plates which are connected to one another along their rear sides facing away from the electrochemical cell. The separators can be used, for example, to electrically contact the electrodes of individual electrochemical cells (e.g. fuel cell cells) and / or to electrically connect adjacent cells (cells connected in series). In the case of fuel cell cells, bipolar plates are usually used as separators.

[0003] The individual plates of the separator may include such a channel structure, which is used to supply one or more media to the battery cells and / or to transport the media away from the battery cells. The medium can be, for example, a fuel (for example, hydrogen or methanol), a reaction gas (for example, air or oxygen) or a coolant as a feed medium, and a reaction product and a heated coolant as a discharged medium. In addition, the separator can also be used to transfer waste heat generated in the electrochemical battery cells, such as waste heat generated during the conversion of electrical energy or chemical energy in a fuel cell, and can be configured to seal various media channels or cooling channels with respect to each other and / or to the outside. In the case of fuel cell cells, the reaction medium is the fuel and the reaction gas, and the reaction medium is usually conducted on the mutually opposite surfaces of the individual plates, while the coolant is conducted between the individual plates. The electrochemical battery cells and in particular the electrochemical battery cells of the fuel cell cells can, for example, each include a membrane electrode assembly (or MEA) with a corresponding polymer electrolyte membrane (PEM) and electrodes. The MEA can also include one or more gas diffusion layers (GDL), which are usually oriented toward the separator and in particular toward the bipolar plates of the fuel cell cell system, and are, for example, in the form of carbon felt.

[0004] The structure and function of the individual plates usually require that the channels of the individual plates of the same partition run in a cross-shaped manner relative to each other at least in certain areas, so that the rear sides of the channel bases are only in contact and connected in the cross-shaped areas. If the individual plates are connected in the cross-channels, this arrangement therefore places high demands on the positioning accuracy of the individual plates relative to each other and on the positioning of the instruments provided for forming the connection relative to the individual plates. Conventional methods for connecting the individual plates to each other are, for example, welding and in particular laser welding, brazing or adhesive bonding. If the required positioning accuracy is not observed when connecting the individual plates, the deviation may lead to a connection that is too weak or at least partially completely lacking a connection. In particular, the pressure of the coolant conducted between the individual plates may then lead to tearing of the connection, which, for example, opens between the plates, or, for example, the welding plug is torn from one or two individual plates, so that a hole is generated in at least one plate. If the joint (joint) is designed as a welded joint (joint), the rapid cooling of the weld pool will usually form a so-called end pit at the end of the weld seam. In particular, in the region of the end pit, star-shaped cracks may occur, which may lead to immediate leakage or reduced durability. Additionally or alternatively, the deviation may cause too much energy to enter a point in the individual plate and burn it through, thereby also producing a hole. The individual plate may therefore be damaged along the connection location to the extent that it cannot be used. This may cause the electrochemical cell cells enclosed between adjacent separators to be flooded with such a cooling fluid that is conducted between the individual plates and passes through the cracks in the individual plates. If both individual plates include holes, uncontrolled reactions between the reaction media may also occur. Both of these situations may lead to failure of the entire stack. To date, methods for connecting individual plates in areas where the channels of the individual plates extend in a cross-like manner may therefore lead to a large number of rejections in production or a short system operating life. Summary of the invention

[0005] The invention is therefore based on the object of providing a separator for an electrochemical system which is as stable as possible even in regions in which the channels of the individual plates of the separator extend in a cross-shaped manner relative to one another and which can be produced with the smallest possible number of rejects.

[0006] This object is achieved by means of a separator for an electrochemical system and an electrochemical system according to the independent claims. Special configurations are described in the dependent claims and in the following description.

[0007] Correspondingly, a separator for an electrochemical system is proposed. The separator comprises a first separate plate and a second separate plate connected to the first separate plate, wherein the two separate plates are in contact with each other in a contact region.

[0008] The first separate plate comprises two first channels for conducting the medium, which are formed into the first separate plate, which run close to each other and which are separated from each other at least in sections by a web formed between the two first channels.

[0009] The second separate plate comprises a second channel for conducting the medium, the second channel being formed in the second separate plate, wherein the web formed between the first channels and the second channel formed in the second separate plate are constructed and arranged such that a projection of the second channel onto the first separate plate perpendicular to the plane of the first separate plate intersects the web along an intersection region of the web.

[0010] The web is lowered in the crossover region of the web so that the first channels running on both sides of the web are fluidly connected by means of the lowered portion of the web. It is further provided that the rear side of the first separate plate in the region of the lowered portion or adjacent to the lowered portion, the rear side facing the second separate plate, is connected by means of a welded joint to the rear side of the base of the second channel in the contact region of the separate plates, the rear side facing the first separate plate. For example, by means of a welded joint, in the contact region of the separate plates, the rear side of the base of the lowered portion facing the second separate plate can be connected to the rear side of the base of the second channel facing the first separate plate.

[0011] The weld joint extends longitudinally from a first end located in the first end region to a second end located in the second end region. The weld joint between the first end and the second end forms an end recess. The end recess is spaced apart from the first end of the weld joint and from the second end of the weld joint.

[0012] Instead of the expression that the projection of the channels and / or webs of the second separate plate on the first separate plate intersects the webs and / or channels of the first separate plate or vice versa, for the sake of simplicity, the shorter expression that the channels and / or webs of the second separate plate intersect the webs and / or channels of the first separate plate or vice versa will be used in some cases below. However, this should always be understood to mean that the mutually intersecting webs and channels of the two separate plates extend in different planes at least in some sections in each case, which planes are oriented predominantly parallel to one another. Unless otherwise stated, the planes of the separate plates refer to their neutral fibers.

[0013] Since the web separating the first channel is lowered at its intersection with the second channel and the rear side of the base of the lowered portion, which rear side faces the second separate plate, is connected in a materially joined manner to the rear side of the base of the second channel, which rear side faces the first separate plate, the area in which the two separate plates are connected or connectable is increased in size. In this way, there is more space for the above-mentioned welded joint, with the result that the latter is larger than in conventional separators, for stabilizing the separator.

[0014] In pressure pulsation tests, in which a medium is forced under high and alternating pressure between the individual layers of the separator in order to test the durability of the separator, it has been shown that the welded joint can crack or even tear open completely in its end region, that is to say at the start and / or end of the welded joint, where the welding tool is started or closed. This tearing open is sometimes also referred to as debonding of the welded joint and generally has a negative impact on the service life of the separator. The end region is therefore generally the weak point of the welded joint.

[0015] The ends of a weld joint may be subject to greater stresses than the areas between the ends of the weld joint, in particular in the case of pulsating pressure stresses caused by the coolant conducted between the individual plates. An advantage of the proposed weld joint design is that the areas of the end pits, where the weld joint usually has a weaker bond, are located at a distance from the particularly stressed ends of the weld joint. In this way, cracks and the resulting leaks can be reduced or even prevented.

[0016] In one embodiment, the weld joint may be designed such that no end recess is formed in the first end region and / or in the second end region.

[0017] The first end region of the weld joint can be defined as an area extending from the first end of the weld joint in the direction of the second end of the weld joint. The first end region can extend from the first end of the weld joint to be closely adjacent to the end pit. The second end region of the weld joint can be defined as an area extending from the second end of the weld joint in the direction of the first end of the weld joint. The second end region can extend from the second end of the weld joint to be closely adjacent to the end pit. Alternatively, the end region can be defined by the area of ​​the weld joint where the welding tool or welding laser beam is applied. Therefore, the end region can be referred to as the approach region of the welding tool or welding laser beam. With the welding tool approaching, for example, two separate plates may not be completely welded together locally in the end region compared to the rest of the weld joint.

[0018] The weld joint may include a first weld seam and a second weld seam that at least partially overlap. The end recess may be arranged in the overlap region. The overlap region may be defined as a region in which the first weld seam at least partially overlaps the second weld seam. For example, the length of the first and / or second end region may correspond to at most twenty times the length of the end recess in the overlap region, preferably at most fifteen times the length of the end recess in the overlap region, and particularly preferably at most twelve times the length of the end recess in the overlap region. For example, the length of the first end region and / or the second end region may correspond to at least 100% of the length of the end recess in the overlap region, preferably at least 150% of the length of the end recess in the overlap region, and particularly preferably at least 200% of the length of the end recess in the overlap region. The length of the first end region and / or the second end region may substantially correspond to the length of the end recess in the overlap region. The length may be measured on the side where the laser beam enters the component during production of the weld joint.

[0019] In one embodiment, the end dimple may be located in the center 85% position, particularly the center 70% position, between the first end and the second end of the weld joint. The advantage of arranging the end dimple in the center region between the first end and the second end of the weld joint is that the end dimple is spaced apart from the particularly stressed end of the weld joint.

[0020] In one embodiment, the weld joint may have a scale in a first direction in the first end region, in particular in the region from the first end of the weld joint to the end recess. The weld joint may have a scale in a second direction opposite to the first direction in the second end region, in particular in the region from the second end of the weld joint to the end recess.

[0021] In one embodiment, the first weld seam may extend from the first end of the weld joint toward the second end of the weld joint, surrounding the end recess and beyond the end recess. The second weld seam may extend from the second end of the weld joint in the direction of the first end of the weld joint, surrounding the end recess, to the end of the end recess facing the first end of the weld joint.

[0022] It should be noted that in the present disclosure, the end recess may be defined such that a welding mirror is surrounded by the end recess.

[0023] The weld joint may be formed by welding a first weld seam in a first direction, wherein an end recess of the first weld seam is formed at the end of the first weld seam. Then, a second weld seam may be welded in a second direction opposite to the first direction. The second weld seam may at least partially overlap the first weld seam. During production of the weld joint, the end recess of the first weld seam may be traversed by the second weld seam, such that the end recess of the second weld seam at least partially overlaps the end recess of the first weld seam, or is preferably located directly beside the traversed end recess of the first weld seam along the weld joint, or is located at a certain distance close to the traversed end recess of the first weld seam along the weld joint.

[0024] The end recess of the second weld seam may form the end recess of the above-mentioned weld joint.

[0025] In one embodiment, the weld joint can be designed such that the first weld seam at least partially overlaps the second weld seam in the overlap region. The center lines of the first weld seam and the second weld seam can be directly above each other or at a distance from each other. For example, the distance between the center line of the first weld seam and the center line of the second weld seam can be at most 25%, preferably at most 20%, particularly preferably at most 15% of the width of the first weld seam and / or the second weld seam. The width of the weld seam refers to the actual width of the weld seam, not the width spanned by the curved section of the weld seam.

[0026] The distance between the end recess and the first and / or second end of the weld joint can be at least 20%, preferably at least 50%, and / or at most 1000%, preferably at most 800% of the width of the first and / or second weld seam.

[0027] The length of the end recess may correspond to at least 25%, preferably at least 40%, and / or at most 600%, in particular at most 400%, in particular at most 250% of the width of the first and / or second weld seam.

[0028] The first weld seam may have a scale in a first direction at least in some sections, and the second weld seam may have a scale in a second direction at least in some sections, wherein the second direction is opposite to the first direction. In particular, the first weld seam only shows a scale in the first direction in the area not overlapped by the second weld seam.

[0029] The length of the overlapping area can correspond to at least 400%, preferably at least 500%, in particular at least 600% of the length of the end recess. The length of the overlapping area can correspond to at least 10% of the length of the welded joint, or to at least 20% of the length of the welded joint, or to at least 30% of the length of the welded joint.

[0030] The length of the overlapping region can correspond to a maximum of 80% or a maximum of 60% or a maximum of 50% or a maximum of 40% or a maximum of 35% of the length of the weld joint.

[0031] In one embodiment, the weld joint may include at least one straight section or have a straight path. For example, the entire weld joint may run in a straight line. Alternatively, a first section of the weld joint may run along a first straight line, and a second section of the weld joint may run along a second straight line. The first weld seam may run completely or partially along the first straight line. The second weld seam may run completely or partially along the second straight line. The first straight line may be substantially parallel to, preferably exactly parallel to, the second straight line. The first straight line and the second straight line may be offset to the side.

[0032] The weld joint may have a first curved portion, wherein the first curved portion extends and is curved such that a virtual straight line extending vertically through the first end region intersects the weld joint at least twice. Alternatively or additionally, the weld joint may have a second curved section, wherein the second curved section extends and is curved such that a second virtual straight line extending vertically through the second end region intersects the weld joint at least twice. Thus, the welding geometry may be designed such that a further section of the weld joint, typically a curved section, runs close to the associated end region, which may stabilize or reinforce the end region of the weld joint.

[0033] The welded joint may be a laser welded joint. Laser welded joints can be produced in a particularly precise manner. However, this document is not limited to laser welded joints.

[0034] The welded joint can be designed as a continuous welded joint, i.e. without interruptions. The separator, in particular the distribution and / or collecting region of the separator, can have a plurality of such welded joints. Preferably, the separator has corresponding welded joints only in the distribution and / or collecting region and not in the electrochemically active region.

[0035] In some embodiments, at least one of the end regions and, for example, the associated curved section merges continuously into each other. For example, it can be provided that the first end region adjoins the first curved section or is a part of the first curved section, and / or the second end region adjoins the second curved section or is a part of the second curved section.

[0036] The shape of the weld joint can be designed so that it can be formed by at most one application of the welding tool and / or the welding laser beam. This has the advantage that the weld joint has only one end pit. Alternatively, the shape of the weld joint can be designed so that it can be formed by repeated applications of the welding tool and / or the welding laser beam. The end pit of a previously applied weld joint can be traversed by a subsequent weld joint.

[0037] As provided, each individual plate generally comprises at least one through-opening for the passage of a fluid, an electrochemically active area, and at least one distribution or collection area, which fluidically connects the through-opening to the electrochemically active area. The first channel is generally arranged in the distribution or collection area of ​​the first individual plate, and the second channel in the distribution or collection area of ​​the second individual plate, and runs at an angle to one another when observing an orthogonal projection onto a common plane parallel to the plate plane. Whether a distribution or collection area is a distribution area or a collection area is generally determined only during operation, since a symmetrical design, in particular a point-symmetrical design, is generally chosen.

[0038] In the application of a fuel cell monomer system, the above separator is usually called a bipolar plate.

[0039] Furthermore, an electrochemical system is proposed, which comprises a plurality of stacked separators or bipolar plates of the above-mentioned type.

[0040] In yet another aspect, a method for producing a separator of the above type is provided. The method comprises the following steps:

[0041] I. providing a first separate plate having two first channels for guiding a medium, the two first channels being formed in the first separate plate, running close to each other and being separated from each other at least in some sections by a web formed between the first channels;

[0042] II. Providing a second separate plate, the second separate plate having a second channel formed in the second separate plate for medium guidance;

[0043] III. Arranging the first and second plates so that a projection of the second channel perpendicular to a plane of the first separate plate onto the first separate plate intersects the web along the intersection region of the web; wherein the web is lowered in the intersection region of the web so that the first channels extending on both sides of the web are in fluid communication via the lowering of the web, and

[0044] IV. The rear side of the countersunk bottom facing the second separate plate is connected to the rear side of the second channel bottom facing the first separate plate by means of a weld joint in the contact area of ​​the separate plates, and the weld joint is designed so that the weld joint extends longitudinally from a first end located in the first end area to a second end located in the second end area, and the weld joint forms an end recess between the first end and the second end, and the end recess is spaced apart from the first end and the second end.

[0045] In step IV, the first weld seam may be welded along a first direction. The second weld seam may be welded in a second direction opposite to the first direction, without the second weld seam overlapping the first weld seam in the overlap region.

[0046] The end recess of the first weld seam can be at least partially, preferably completely traversed by the second weld seam. In this way, a continuous weld joint having only one end recess can be generated, which is spaced apart from the first end of the weld joint and from the second end of the weld joint. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Exemplary embodiments of separators and electrochemical systems are shown in the accompanying drawings and will be explained in more detail according to the following description. In the drawings:

[0048] Figure 1 schematically illustrates a perspective view of an electrochemical system including a plurality of separators or bipolar plates arranged in a stack;

[0049] Figure 2 Schematically shows the Figure 1 A perspective view of two bipolar plates of a system, wherein a membrane electrode assembly (MEA) is arranged between the bipolar plates;

[0050] Figure 3 Schematically shows the Figure 1 The system's approach to the cross-section of the system's plate stacking;

[0051] Figure 4A is a schematic cross-section of a top view of a collection or distribution area of ​​a partition, whereby the webs and channels on the rear side of the partition are visible;

[0052] Figure 4B Schematically shows Figure 4A A cross-sectional view of the section AA indicated in ;

[0053] Figure 5 schematically shows a cross section of a top view of a separator of a first separate plate and a second separate plate, wherein the channels of the two separate plates are visible and the first separate plate is connected to the second separate plate by means of a welded joint;

[0054] Figures 6A to 6C Various embodiments of welded joints are shown; and

[0055] Figure 6C 'Schematically shows Figure 6C The indicated passage Figure 6C Height profile of the profile BB of the end pit;

[0056] Figure 7shows the view from the beam entry side, including Fig. 6A A cross-section of a top view of a welded joint of a separate plate of the bulkhead;

[0057] Figure 8 Shown is a view from the rear side, including Fig. 6A A cross-section of a top view of a welded joint of a separate plate of the bulkhead;

[0058] Fig. 9 schematically shows a cross section through the weld joint of the bulkhead of FIG. 4 in an area without end recesses; and

[0059] Fig.10 A section through the weld joint of the separator of FIG. 4 in the region where the end recess is located is schematically shown.

[0060] Here and below, features that appear repeatedly in different figures are in each case denoted by the same or similar reference numerals. For the sake of clarity, reference is sometimes made to the complete set of figures (e.g., FIG. 4 instead of FIG. Figure 4A-4B one). DETAILED DESCRIPTION

[0061] Figure 1 An electrochemical system 1 is shown, which comprises a plurality of structurally identical metal separators or 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 the stacking direction. In the present example, the system 1 is a stack of fuel cell cells. Two adjacent bipolar plates 2 of the stack in each case enclose an electrochemical cell cell between them, which is used, for example, to convert chemical energy into electrical energy. In order to form an electrochemical cell cell of the system 1, a corresponding membrane electrode assembly (MEA) is arranged between adjacent bipolar plates 2 of the stack (see, for example Figure 2 ). Each MEA generally includes at least one membrane, such as an electrolyte membrane. A gas diffusion layer (GDL) may also be arranged on one or both surfaces of the MEA ( Figure 1 and Figure 2 (not shown in the figure).

[0062] In alternative embodiments, the system 1 may likewise be in the form of an electrolyzer, an electrochemical compressor or a redox flow battery. In these electrochemical systems, separators may likewise be used. Although the medium conducted on or through the separators in the case of an electrolyzer, in an electrochemical compressor or in a redox flow battery may in each case be different from the medium used for a fuel cell monomer system, the structure of these separators may correspond to the structure of the separator 2 described in detail herein.

[0063] The z-axis 7 together with the x-axis 8 and the y-axis 9 define a right-handed Cartesian coordinate system. The partitions 2 each define a plate plane, each of the plate planes of the individual plates being oriented parallel to the xy plane and thus perpendicular to the stacking direction 7 or z-axis 7. The end plate 4 comprises a plurality of medium connections 5 via which a medium can be fed to the system 1 and via which a medium can be discharged from the system 1. These media that can be fed to the system 1 and discharged from the system 1 can include, for example, fuels such as molecular hydrogen or methanol, reaction gases such as air or oxygen, reaction products such as water vapor or depleted fuel, or coolants such as water and / or ethylene glycol.

[0064] Figure 2 Shown in stereogram form Figure 1 Two adjacent separators 2 of an electrochemical system of the type of system 1, and a membrane electrode assembly (MEA) 10 known in the prior art arranged between the two adjacent separators 2, Figure 2 The MEA 10 is largely hidden by the separator 2 facing the viewer. The separator 2 is formed by two separate plates 2a and 2b, which are joined together in a material connection (see for example Figure 3 ), where only the first individual panel 2a facing the observer and hiding the second individual panel 2b is in Figure 2 The individual plates 2a, 2b can each be made of a metal sheet, for example a stainless steel sheet. The individual plates 2a and 2b can be welded to each other by, for example, laser welding the joints.

[0065] The individual plates 2a and 2b comprise through-openings which are aligned with one another and form through-openings 11a-11c in the partition 2. When a plurality of partitions of the type of partition 2 are stacked, the through-openings 11a-11c form lines extending through the stack 6 in the stacking direction 7 (see Figure 1 ). Typically, each of the lines formed by the through-openings 11a-11c is fluidically connected to one of the ports or media connections 5 in the end plate 4 of the system 1. By means of the lines formed by the through-openings 11a, for example, a coolant can be introduced into the stack or discharged from the stack. Conversely, the lines formed by the through-openings 11b, 11c can be configured to supply fuel and reaction gases to the electrochemical cells of the fuel cell cell stack 6 of the system 1 and to discharge reaction products from the cell stack. The through-openings 11a-11c for medium conduction are substantially parallel to the plate plane.

[0066] In order to seal the through-openings 11a-11c with respect to the interior of the stack 6 and with respect to the environment, the first individual plates 2a each comprise a sealing arrangement in the form of a sealing bead 12a-12c, which is each arranged around the through-opening 11a-11c and each completely surrounds the through-opening 11a-11c. Figure 2 On the rear side of the viewer in the embodiment, corresponding sealing beads (not shown) for sealing the through openings 11a-11c are included. Alternatively, an elastomeric seal may be used.

[0067] In the electrochemically active region 18, the first individual plates 2a are arranged on their facing sides. Figure 2 On the outside of the observer there is a flow field 17 with structures for guiding the reaction medium along the outside of the individual plates 2a. Figure 2 In the embodiment, these structures are provided by a plurality of webs and channels running between and defined by these webs. Figure 2 On the outer side of the observer, the first individual plates 2a each also have a distribution and collection area 20. The distribution or collection area 20 in each case comprises structures which are configured to distribute the medium introduced into the distribution area 20 from the first of the two through-openings 11b over the entire active area 18 or to collect or combine the medium flowing from the active area 18 toward the second through-opening 11b. The fluid guiding structures 29 of both the distribution or collection areas 20 are also located in Figure 2 The distribution area 20 is provided by webs and channels running between the webs and bounded by the webs. In the following, for simplicity, only the distribution area 20 will be discussed; a corresponding description also applies to the collection area 20.

[0068] The sealing ridges 12a-12c have passages 13a-13c, wherein the passage 13a is formed on both the lower side of the upper individual plate 2a and the upper side of the lower individual plate 2b, while the passage 13b is formed in the upper individual plate 2a, and the passage 13c is formed in the lower individual plate 2b. For example, the passage 13a is designed as a local protrusion of the ridge, allowing the coolant to pass between the through opening 12a and the distribution area 20, allowing the coolant to enter the distribution area between the partitions, or to be drawn out from the collection area 20. In addition, the passage 13b enables hydrogen to pass between the through opening 12b and the distribution area on the top side of the upper individual plate 2a, and these passages 13b are characterized by perforations facing the distribution area and running obliquely relative to the plate plane. Thus, for example, hydrogen flows through the passage 13b from the through opening 12b to the distribution area on the top side of the upper individual plate 2a, or flows from the collection area in the opposite direction. The passage 13c enables, for example, air to pass between the through-opening 12c and the distribution area, so that the air passes into the distribution area on the underside of the lower individual plate 2b or is conducted out of the collection area. The relevant perforations are not visible here.

[0069] The first individual plates 2a also each have a further sealing arrangement in the form of a peripheral bead 12d which runs around the flow field 17 of the active area 18, the distribution and collecting area 20 and the through-openings 11b, 11c and seals them to the through-opening 11a, i.e. to the coolant circuit, and to the environment of the system 1. The second individual plates 2 each comprise a corresponding peripheral bead. The structure of the active area 18, the distribution structure of the distribution area and the collecting area 20 and the sealing bead 12a-12d are each formed in one piece with the individual plate 2a and are each formed into the individual plate 2a in an embossing process or a deep drawing process or by means of hydroforming. The same applies to the corresponding structure of the second individual plate 2b.

[0070] The two through-openings 11b or the lines formed by the through-openings 11b through the plate stack of the system 1 each face the first individual plate 2a via a passage 13b in the sealing collar 12b, via a distribution structure of the distribution or collecting area 20, and via the Figure 2 Similarly, the two through-openings 11c or the pipelines formed by the through-openings 11c through the plate stack of the system 1 each lead away via a corresponding flange passage, via a corresponding distribution and collection structure and via a second separate plate 2b. Figure 2The through-openings 11a or the lines formed by the through-openings 11a through the plate stack of the system 1 are fluidically connected to each other via cavities 19 enclosed by the individual plates 2a and 2b. The cavities 19 are used in each case to conduct a coolant through the separator 2 and in particular to cool the electrochemically active regions 18 of the separator 2.

[0071] Figure 3 Schematically shows the Figure 1 The section plane is oriented in the z-direction and is therefore perpendicular to the plate plane of the partition wall 2. Figure 3 In the example, the section plane runs along the curved section, i.e. along Figure 2 The cutting line CC in the figure proceeds.

[0072] The stacked, structurally identical separators 2 each comprise the above-mentioned first metal individual plate 2a and the above-mentioned second metal individual plate 2b. Structures for guiding the medium along the outer surface of the separator 2 are evident, these structures here in particular in each case in the form of webs and channels defined by the webs. In particular, channels on the surfaces of the individual plates 2a and 2b adjacent to each other, which surfaces are oriented away from each other, and cooling channels in the cavity 19 between the individual plates 2a and 2b adjacent to each other are shown. Between the two cooling channels in the distribution or collection area 20 and in the active area 18, the two individual plates 2a and 2b are superimposed on each other in the contact area 24 and are connected to each other in each case in said contact area, in this example by means of a laser weld.

[0073] A corresponding membrane electrode assembly (MEA) 10, such as is known from the prior art, is arranged between adjacent separators 2 of the stack. The MEA 10 generally comprises a membrane, such as an electrolyte membrane, and an edge portion 15 connected to the membrane 14. For example, the edge portion 15 may be bonded to the membrane 14, such as by an adhesive connection or by lamination.

[0074] The membrane of the MEA 10 extends in each case at least over the active area 18 of the adjacent separator plates 2 and enables the transfer of protons over or through the membrane 14. However, the membrane does not reach into the distribution or collection area 20. The edge sections 15 of the MEA 10 serve in each case to position, secure and seal the membrane between the adjacent separator plates 2.

[0075] The edge portion 15 in each case covers the distribution or collection area 20 of the adjacent partition 2. The edge portion 15 can also extend outwards beyond the peripheral flange 12d and abut or protrude beyond the outer edge area of ​​the individual plates 2a and 2b (see Figure 2 ).

[0076] Furthermore, a gas diffusion layer 16 can be additionally arranged in the active region 18. The gas diffusion layer 16 can guide the flow to the membrane over the largest possible area of ​​the surface of the membrane and can thus improve the proton transfer through the membrane. The gas diffusion layer 16 can in each case be arranged, for example, on both sides of the membrane in the active region 18 between adjacent separators 2. The gas diffusion layer 16 can be formed, for example, by a fiber mat or include a fiber mat.

[0077] Also refer to Figure 4A , in which a section of a distribution or collection area 20 is shown. The distribution or collection area 20 of the second separate plate 2b and the first separate plate 2a are connected to each other in a materially joined manner in certain areas along their mutually facing rear sides, in particular here by a laser welded joint 50'. Figure 4A As shown, the channels 30, 31 and the webs 32 of the distribution area 20 of the first individual plate 2a and the channels 40 and the webs 42 of the distribution area 20 of the second individual plate 2b extend crosswise to one another in parallel planes. Figure 4A In the example, the channels 30, 31 and the webs 32 in the distribution area 20 of the first separate plate 2a form an intersection angle with the channels 40 and the webs 42 in the distribution area 20 of the second separate plate 2b, which is approximately between 40° and 60° or between 120° and 140°.

[0078] Such a region of the web of the first separate plate 2a, in which the vertical projection of one of the channels of the second separate plate 2b onto the first separate plate 2a intersects with one of the webs of the first separate plate 2a, is referred to as the intersection region 33 of the web 32 of the first separate plate 2a. In full correspondence, such a region of the web of the second separate plate 2b, in which the vertical projection of one of the channels 30, 31 of the first separate plate 2a onto the second separate plate 2b intersects with one of the webs of the second separate plate 2a, is referred to as the intersection region of the web of the second separate plate 2b.

[0079] As mentioned in the introduction, an important disadvantage of the known partition 2 is that in the area where the channels of the separate plates 2a and 2b extend in a crossing manner as described herein, the separate plates 2a and 2b of the partition 2 are generally connected only along a small contact area, specifically, precisely at the position where the mutually facing rear sides of the channel bases of the two separate plates 2a and 2b intersect each other.

[0080] In order to solve this problem, the publication WO2017 / 029158A1 proposes to expand the contact area of ​​each plate 2a, 2b, which is achieved by making the contact area of ​​each plate 2a, 2b Figure 4A and Figure 4BThe web 32 of the first individual plate 2a shown is lowered in lowered areas 34 in some intersection regions 33, so that in these intersection regions 33, the rear side of the first individual plate 2a facing the second individual plate 2b is in contact with the rear side of the bottom of the corresponding channel 40 of the second individual plate 2b and is connected in a material-locked manner, here for example by a laser welded joint 50'. The rear sides of the individual plates 2a and 2b are in contact in the distribution area 20 and are or can be connected to one another along a contact surface, which can therefore be significantly increased in size.

[0081] In particular, the two separate plates 2a and 2b are or can be connected to one another not only at the locations where the channels 30, 31 of the first separate plate 2a and the channels 40 of the second separate plate 2b intersect one another and their rear sides thus contact one another, but also additionally in the intersection region 33 of the web 32 between the channels 30, 31 of the first separate plate 2a, where the lowered portion 34 of the web 32 provides a larger contact surface between the rear sides of the separate plates 2a and 2b. This increases the stability of the connection between the separate plates 2a and 2b and reduces the requirements for the spatial accuracy of the selected connection technology. The rejection rate during the production of the separator 2 and the service life of the separator 2 in operation can thus be improved.

[0082] Since the first channels 30 and 31 extending on both sides of the web 32 are fluidly connected by means of the lowered portion 34 of the web 32, the positioning of the lowered portion 34 along the first channels 30 and 31 can also be used in a targeted manner to influence the flow behavior of the medium in the first channels 30 and 31 and in the intermediate space 19 between the separate plates 2a and 2b.

[0083] Despite the above measures, pressure pulsation tests carried out by the applicant have shown that welded joints may form weak points in the diaphragm 2. When high fluid pressures are applied, welded joints sometimes develop cracks at their start and end points.

[0084] The present invention is therefore intended to further improve the durability of the partition plate 2. In particular, the use of the welded joint 50' is intended to achieve a higher service life, at least in terms of the operating pulsations of the pressure of the medium, in particular the coolant, that are present. The welded joint 50' extends longitudinally from a first end 51 in the first end region to a second end 61 in the second end region. The welded joint 50 forms an end recess 63 between the first end 51 and the second end 61. The end recess 63 is spaced apart from the first end 51 of the welded joint 50' and from the second end 61 of the welded joint 50'.

[0085] The weld joint 50' has a first weld seam 50, a second weld seam 60, and an end dimple 63. The first weld seam 50 is welded in a first direction starting from the first end 51 in the direction of the second end 61. The second weld seam 60 is welded in a second direction starting from the second end 61 in the direction of the first end 51. The length of the first weld seam 50 measured from the first end 51 in the direction of the second end extends beyond the end dimple 63, but does not reach as far as the second end 61. The second weld seam 60 starts at the second end and extends around the end dimple 63 to an end of the end dimple 63 that is closer to the first end 51. The end dimple 63 of the weld joint 50' is an end dimple formed by pausing at the end of the second weld seam 60 during welding of the second weld seam 60. The end dimple of the first weld seam 50 is crossed by the second weld seam 60, and thus Figure 4A Not visible in Figure 4A In the example shown, the first weld seam 50 and the second weld seam 60 run along a straight line. In other examples, the first weld seam 50 and / or the second weld seam 60 can include a curved portion.

[0086] Although Figure 4A The weld joint 50' shown in FIG. 1 is straight throughout its length, but Figure 5 The weld joint 50 ′ shown in FIG. 5 may include at least one curved section 54 , 64 , the function of which is to stabilize the weld joint 50 .

[0087] It will be understood that although Figure 4A Only a right-angled form of the weld joint 50 ′ is shown, but the weld joint 50 ′ may alternatively be curved or partially curved. Figure 5 An exemplary embodiment of a weld joint 50 ′ with two bend sections 54 , 64 is shown.

[0088] In particular, Figure 5 The weld joint 50' has a first end region 52 and a first curved section 54. The first curved section 54 extends and curves such that a virtual straight line passing vertically through the first end region 52 intersects the weld joint 50 at least twice, for example in the end region 52 and in the region of the first curved section.

[0089] Alternatively or additionally, the weld joint 50 ′ has a second end region 62 and a second bend section 64 , wherein the second bend section 64 extends and bends such that a second virtual straight line 61 vertically passing through the second end region 62 intersects the weld joint 50 ′ at least twice.

[0090] The virtual straight line is a dotted line drawn vertically through the end regions 52, 62. Depending on the design of the bending region, the weld joint is more or less intersected by the virtual straight line. In other words, a portion of the weld joint 50 runs close to the end regions 52, 62, thereby reinforcing the latter. For example, the curved sections 54, 64 can have various shapes: circular, spiral, at least partially following an ellipse or oval shape, or hairpin-shaped.

[0091] The end regions 52, 62 of the welded joint 50 are defined so as to mark the point where the welding tool is applied, i.e. the start of the welding step. The curved regions 54, 64 locally reinforce the end regions 52, 62, as a result of which the end regions 52, 62 can be stabilized. At least some parts of the curved regions 54, 64 run transversely relative to the end regions and preferably also transversely relative to the flow direction of the fluid. Instead of Figure 4A The narrow end of the weld joint 50' is shown, which results in a significantly wider contact surface compared to the width of the weld joint 50', see Figure 5 , when the operating pressure fluctuates, it cannot be peeled open by the pressure pulsation, or it is quite difficult to peel open. As a result, the peeling open or tearing of the end areas 52, 62 is less likely to occur.

[0092] The weld joint 50' may have a straight central section connected to a first curved section 54 and / or a second curved section 64, see Figure 5 . The end recesses 63 are preferably arranged in the central section. Instead of a straight central section, a corrugated or non-straight central section can also be arranged between the two curved portions 54, 64 or adjacent to the curved sections 54, 64. At least one section of the central section can also be straight, and at least one other section of the central section can be non-straight. The length of the middle section can be at least 40%, at least 50% or at least 60% of the length of the entire weld joint 50'. For example, the length of the middle section can be 2.5 mm, and the total length of the weld joint 50' is about 3.5 mm, wherein the latter does not represent the non-curled length, but rather represents an extension along a straight line parallel to the straight middle section. For example, the end regions 52, 62, in particular their straight portions, can extend substantially parallel to the central section and / or form an extension of the central section.

[0093] and Figure 4A Compared to the straight weld line 50' in FIG. 4 , the curved sections 54, 64 require more space in the lateral direction, ie transversely to the longitudinal extension of the channel 40. Figure 4AIn the case of narrow channels in the welding joint 50 ′, such space is not always available, which may have a limiting effect on the geometry of the welding joint 50 ′. The channels 30 , 31 , 40 can optionally be adapted to the welding joint 50 ′ in terms of their geometry, with the result that the channels 30 , 31 , 40 and the welding joint 50 ′ can match each other. This can be achieved in Figure 5 Seen in.

[0094] exist Figure 5 As is evident in the drawings, the first channels 30, 31 each comprise a first channel widening 36, thereby increasing the size of the contact area 25 of the individual plates 2a, 2b and providing space for the weld joint 50' and in particular the bent portions 54, 64 of the weld joint 50'. The respective channel widening 36 comprises a concave portion 37 in the web 35, adjacent to the web 32 and delimiting the respective channel 30 and 31, which concave portion 37 can be formed as a bulge in the web 35. Here, the width of the web 35 measured perpendicularly with respect to the longitudinal extent of the channels 30, 31 can remain substantially constant. Since the second channel 40 extends in an angled manner with respect to the first channels 30, 31, the channel widenings 36 are preferably arranged offset with respect to each other in the longitudinal direction or extent direction of the channels 30, 31. By means of the weld joint 50 ′ and in particular the bent portions 54 , 64 of the weld connection, the first separate plate 2a is thus connected in the region of the first channel widening 36 to the second separate plate 2b and in particular to the channel base of the second channel 40 .

[0095] exist Figure 5, the second channel 40 comprises at least one second channel widening 46 in a second region adjacent to the intersection region 33 of the web 32. The channel widening 46 may form a concave portion 47 or a concave bulge 47 in the web 42 that delimits the channel 40. The contact area 25 of the separate plates 2a and 2b may extend at least partially into the region of the second channel widening 46. The second separate plate 2b may be provided to be connected to the first separate plate 2a in the region of the second channel widening 46 by means of a welded joint 50' and in particular a bent portion 54, 64. Optionally, the second channel 40 may have the aforementioned second channel widening 46 on both sides of the intersection region 33. In some cases, the second channel 40 comprises a channel taper 48 in relation to the channel widening 46 in the intersection region 33 between the second channel widenings 46. Here, the channel taper 48 may taper only in relation to the channel widening 46 and may have a width corresponding to the width of the channel 40 outside the channel widening 46. It can be advantageous that the first channel widening 36 and the second channel widening 46 at least partially overlap in the contact area 25. In this case, the weld joint 50' can be arranged in the overlapping area of ​​the described channel widenings 36, 46. The central section can be substantially parallel to the second channel 40. It is also feasible for the middle section to extend at least between the two channel widenings 46. In particular, the central section can be arranged at least in the lowered area 34 of the web 32. The end areas 52, 62 and the bends 54, 64 can be arranged in the channel base of the respective channel 30, 31, 40, and in particular in the area of ​​the channel widenings 36, 46.

[0096] Figures 6A to 6C Various configurations of welded joints 50' are shown, such as may be used in FIG. 4 or Figure 5 In the partition 2 shown. Fig. 6A The weld joint 50' comprises a first weld seam 50 which is welded in a first direction represented by the direction of arrow I and welded along a first imaginary straight line starting from a first end 51 of the weld joint 50'. The first weld seam 50 terminates in a first end recess 53 which is only Fig. 6A The length of the first welded joint 50 is indicated by the length of the directional arrow I. Fig. 6A The weld joint 50' includes a second weld seam 60 that is welded in a second direction represented by the direction of arrow II, starting from a second end 61 of the weld joint 50' and welded along the same first imaginary straight line. The second weld seam 60 overlaps the first weld seam 50 and is welded so as to extend beyond the first end recess 53. The second weld seam ends in the second end recess 63. Fig. 6A, the end recess 63 is arranged substantially centrally between the first end 51 and the second end 61. The length of the second weld seam 60 is indicated by the length of the directional arrow II. The width of the first weld seam 50 substantially corresponds to the width of the second weld seam 60 and the width of the weld joint 50'.

[0097] Figure 6B The weld joint 50' comprises a first weld seam 50 which is welded in a first direction represented by the direction of arrow I and welded along a first imaginary straight line starting from a first end 51 of the weld joint 50'. The first weld seam 50 terminates in a first end recess 53 which is only Figure 6B The length of the first welded joint 50 is indicated by the length of the directional arrow I. Figure 6B The weld joint 50' includes a second weld seam 60, which is welded in a second direction represented by the direction of arrow II, and welded along a second imaginary straight line starting from the second end 61 of the weld joint 50'. The first imaginary straight line and the second imaginary straight line correspond to the center lines of the first weld seam 50 and the second weld seam 60. The first imaginary straight line and the second imaginary straight line are parallel to each other, but have a certain distance from each other. The second weld seam 60 overlaps with the first weld seam 50 and is welded so as to extend beyond the first end recess 53. The second weld seam terminates in the second end recess 63. Figure 6B 60 . The end recess 63 is also arranged substantially centrally between the first end 51 and the second end 61. The length of the second weld seam 60 is indicated by the length of the directional arrow II. The width of the first weld seam 50 substantially corresponds to the width of the second weld seam 60. The width of the weld joint 50 'can vary. In the overlap region where the first weld seam 50 and the second weld seam 60 overlap, the weld joint has a maximum width.

[0098] Figure 6C Welded joint 50' with Fig. 6A The weld joint of is substantially corresponding, wherein the end recess 63 completely coincides with the end recess 53 and is arranged closer to the first end 51 than to the second end 61. In this example, the end recess 63 is about one end recess length away from the first end 51.

[0099] Figure 6C 'Scheme showing the Figure 6C The cross section BB shown is through the weld joint 50' and Figure 6C Graph K shows the height profile of the weld seam in a cross section over its length in the region of the end recess 63. The double arrow indicates the length of the end recess 63. In the region outside the end recess 63, the surface of the weld seam is noisy, while the surface in the end recess 63 is smoother.

[0100] Figure 7 Shown according to Figure 4A 2, as viewed from the beam entry side, ie from plate 2b. The welded joint 50' is shown corresponding to Fig. 6A The first weld seam 50 has a first scale-like portion in a region not overlapping with the second weld seam, and the second weld seam has a second scale-like portion in a direction opposite to the first scale-like portion.

[0101] Figure 8 The welded joint 50' Figure 7 The section of the top view of the individual plates of the partition 2, the view is on the side from which the light beam leaves, ie on the rear side of the individual plate 2a. The welded joint is located in the region of the lowering 34 of the web 32.

[0102] Fig. 9 and 10 Each shows a schematic section through a partition 2 in the region of an exemplary weld joint 50 ′. The sections are substantially perpendicular to the direction of the weld joint 50 ′. Fig. 9 A region is shown in which the weld joint 50' extends through the entire material thickness of the second plate 2b, but only through approximately one third of the material thickness of the first plate 2a. Fig.10 The weld seam 50' in FIG. 2 is shown in an area that completely passes through the material thickness of the second plate 2b and the first plate 2a. The weld seam 50' thus extends from the outer side 22 of the first plate 2a to the outer side 23 of the second plate 2b. Fig. 9 As shown, the weld joint can also be visible only on one of the two outer sides 22, 23 and not extend all the way to the respective other outer side 23, 22. Fig. 9 and 10 As indicated, the first individual plate 2a and / or the second individual plate 2b may have a thickness of at least 50 μm, in particular at least 70 μm. The thickness of each plate may also be at most 200 μm, in particular at most 150 μm, in particular at most 100 μm. In view of these relatively small thicknesses, as Fig. 9 As shown, the weld joint 50 ′ may be in the form of a through-weld.

[0103] It should be mentioned again that the separator 2 described above and shown in the figures is usually referred to as a bipolar plate in the application of the fuel cell monomer system 1 .

[0104] Furthermore, an electrochemical system 1 is proposed, for example Figure 1 Of the type shown, the system comprises a plurality of stacked separators 2 or bipolar plates of the type described herein.

[0105] It is understood that the features of the embodiments of the aforementioned figures may be claimed in combination with each other or individually, as long as they are not contradictory to each other.

[0106] List of reference numerals:

[0107] 1 Electrochemical system

[0108] 2 Separator or bipolar plate

[0109] 2a Separate board

[0110] 2b Separate board

[0111] 3 End plate

[0112] 4 End plate

[0113] 5 Media ports

[0114] 6 stacks

[0115] 7 z direction

[0116] 8 x direction

[0117] 9 y direction

[0118] 10. Membrane Electrode Assembly

[0119] 11a-11c through opening

[0120] 12a-12d Sealing flange

[0121] Pathway 13a-13c

[0122] 14 Membrane

[0123] 15 Edge part.

[0124] 16 Gas Diffusion Layer

[0125] 17 Flow Field

[0126] 18 Electrochemically active area

[0127] 19 Cavity

[0128] 20 Distribution or collection area

[0129] 22 The outer side of the first separate plate 2a

[0130] 23 The outer side of the second separate plate 2b

[0131] 25 contact areas

[0132] 29 Fluid guiding structure of distribution or collection area

[0133] 30 First Channel

[0134] 31 First Channel

[0135] 32 belly plate

[0136] 33 Intersection area

[0137] 34 Lowered portion of the web

[0138] 35 belly plate

[0139] 36 First channel widening part

[0140] 37 Concave area

[0141] 40 Second channel

[0142] 42 belly plate

[0143] 46 Second channel widening part

[0144] 47 Concave area

[0145] 48 Channel taper

[0146] 50' welding joint

[0147] 50 First weld seam

[0148] 51 First end of welded joint

[0149] 52 first end region

[0150] 53 End pit of first weld seam

[0151] 54 First bend

[0152] 60 Second welding seam

[0153] 61 Second end of welded joint

[0154] 62 Second end region

[0155] 63 Second weld seam and end pit of weld joint

[0156] 64 Second bending section

[0157] K-curve chart

Claims

1. A separator (2) for an electrochemical system (1), comprising a first separate plate (2a) and a second separate plate (2b) connected to the first separate plate (2a), wherein: The two separate plates (2a, 2b) are in contact with each other in a contact area (25), wherein the first separate plate (2a) comprises two first channels (30, 31) for conducting a medium, the first channels being formed in the first separate plate (2a), the first channels extending close to each other and the first channels being separated from each other at least in some sections by a web (32) formed between the first channels (30, 31); wherein the second separate plate (2b) comprises a second channel (40) for conducting a medium, the second channel being formed in the second separate plate (2b); and wherein the web (32) formed between the first channels (30, 31) and the second channel (40) formed in the second separate plate are constructed and arranged so that a projection of the second channel (40) on the first separate plate (2a) is perpendicular to the plane of the first separate plate (2a) and intersects the web (32) along an intersection region (33) of the web (32); wherein the web (32) is lowered in the intersection region (33) of the web (32) so that the first channels (30, 31) extending on both sides of the web (32) are fluidically connected by means of the lowered portion of the web (32), and wherein the rear side of the base of the lowered portion (34) facing the second separate plate (2b) is connected to the rear side of the base of the second channel (40) facing the first separate plate (2a) by means of a welded connection (50'), in the contact area (25) of the separate plates (2a, 2b), The weld joint (50') extends longitudinally from a first end (51) located in a first end region (52) to a second end (61) located in a second end region (62), wherein the weld joint (50') forms an end recess (63) between the first end (51) and the second end (61), and the end recess (63) is spaced apart from the first end (51) and the second end (61).

2. The separator (2) according to claim 1, characterized in that The weld joint (50') does not form an end recess (63) in the first end region (52) and / or the second end region (62).

3. A separator (2) according to any one of the preceding claims, characterized in that The end recess is located in the center 85% position, in particular the center 70% position, between the first end (51) and the second end (61) of the weld joint (50').

4. A separator (2) according to any one of the preceding claims, characterized in that The weld joint (50') has a scale-like portion in a first direction in the first end region, in particular in the region from the first end of the weld joint to the end recess, and has a scale-like portion in a second direction opposite to the first direction in the second end region, in particular in the region from the second end of the weld joint to the end recess.

5. A separator (2) according to any one of the preceding claims, characterised in that The weld joint (50') includes a first weld seam (50), which extends from the first end of the weld joint (50') toward the second end of the weld joint (50'), surrounds the end recess (63) and exceeds the end recess (63), and the weld joint (50') includes a second weld seam (60), which extends from the second end of the weld joint (50') toward the first end of the weld joint (50'), surrounds the end recess (63), and reaches the end of the end recess (63) facing the first end of the weld joint (50').

6. A separator (2) according to the preceding claim, characterised in that The weld joint (50') is formed such that the first weld seam at least partially overlaps the second weld seam in an overlapping region.

7. A separator (2) according to any one of the preceding claims, characterised in that The distance from the end recess to the first end and / or the second end of the weld joint (50') is at least 20%, preferably at least 50%, and / or at most 1000%, preferably at most 800% of the width of the first weld seam and / or the second weld seam.

8. A separator (2) according to any one of the preceding claims, characterised in that The length of the end recess corresponds to at least 25%, preferably at least 40%, and / or at most 600%, in particular at most 400%, in particular at most 250% of the width of the first weld seam and / or the second weld seam.

9. A separator (2) according to any one of the two preceding claims, characterised in that The first weld seam (50) has scaling in the first direction at least in some sections, and the second weld seam (60) has scaling in the second direction at least in some sections, wherein the second direction is opposite to the first direction.

10. A separator (2) according to any one of the preceding claims, characterised in that The length of the overlapping area corresponds to at least 400%, preferably at least 500%, in particular at least 600% of the length of the end recess.

11. A separator (2) according to any one of the preceding claims, characterised in that The length of the overlapping area corresponds to at most 80% or at most 60% or at most 50% or at most 40% or at most 35% of the length of the weld joint.

12. The assistant (2) according to any one of the preceding claims, characterized in that The length of the overlapping area corresponds to at least 10% of the length of the weld joint or at least 20% of the length of the weld joint or at least 30% of the length of the weld joint.

13. A separator (2) according to any one of the preceding claims, characterised in that The weld joint (50') comprises a straight section or has a straight course.

14. A separator (2) according to any one of the preceding claims, characterised in that The welded joint (50') is a laser welded joint.

15. A separator (2) according to any one of the preceding claims, characterised in that The weld joint (50') is formed as a continuous weld joint.

16. A separator (2) according to any one of the preceding claims, characterised in that The shape of the weld joint (50') is designed so that it can be formed by at most one application of a welding tool and / or a welding laser beam.

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

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