DE102022106374A1 - Bipolar plate and method for producing a bipolar plate - Google Patents

Abstract

A bipolar plate (1) intended for use in a stack of electrochemical cells, in particular a fuel cell stack, comprises two half-sheets (2, 3) lying one on top of the other, through which an active field (7), a distribution field (8), and a number of ports (4, 5, 6) are formed for the passage of media. At least one of the two half-sheets (2, 3) has a folded area (23) adjacent to one of the ports (4, 5, 6), in which flow channels (15, 16) are formed for one of the media, in particular a cooling medium .

Description

The invention relates to a bipolar plate intended for use in a stack of electrochemical cells, in particular in a fuel cell stack. The invention further relates to a method for producing a bipolar plate.

A bipolar plate separates a half-cell of a first electrochemical cell from a half-cell of an adjacent cell in a stack of electrochemical cells. This applies to fuel cells as well as to redox flow cells or electrolysis cells for producing hydrogen.

The US 2011/0195332 A1 discloses stacked arrangements of bipolar plates in fuel cells, with active areas, i.e. active fields, supply areas, which are also generally referred to as distribution fields, and various inlet and outlet openings, i.e. ports, being formed by the bipolar plates. The bipolar plates are made up of anode plates and cathode plates, which are also referred to as half sheets. In the case of the, there are between the half sheets US 2011/0195332 A1 including porous spacers.

One in the US 2011/0177429 A1 The disclosed plate of a fuel cell is designed as a fluid flow plate, with a support frame present as a separate element being arranged at the transition between a port and fluid channels of the flow plate extending from it. The support frame is annular and includes a pair of mutually parallel support walls that are arranged on two sides of the fluid channels. Another possibility of inserting a separate element with a flow-conducting and/or static function into a flow plate of a fuel cell is in US 6,410,179 B1 described. In this case, the separate element also provides a groove for inserting a seal.

Further options for designing flow-conducting or other elements in fuel cells are, for example, in the documents US 2011/0033782 A1 , US 2002/0172852 A1 , DE 10 2014 225 160 A1 and US 2015/0200404 A1 disclosed. In the latter case, a connecting section of an electrically conductive component is bent into a U-shape, with a spacer being located between the two U-legs.

The invention is based on the object of achieving progress over the stated prior art in the production of bipolar plates, with the aim of achieving a particularly favorable relationship between manufacturing effort and geometric precision, function and stability of the end product, i.e. stack of electrochemical cells including biopolar plates.

This object is achieved according to the invention by a bipolar plate intended for use in a stack of electrochemical cells, in particular fuel cells, with the features of claim 1. The object is also achieved by a method for producing a bipolar plate according to claim 8. In the following in connection with The embodiments and advantages of the invention explained in the manufacturing process also apply mutatis mutandis to the devices, i.e. the bipolar plate and the cell stack, and vice versa.

The bipolar plate is constructed in a known basic concept from two half-sheets lying one on top of the other, with the half-sheets forming an active field on each side of the bipolar plate, in which the desired electrochemical reactions take place within the completed cell stack comprising numerous bipolar plates. In a typical design, the active fields take up the majority of the area of each bipolar plate. Furthermore, the bipolar plates form a distribution field and a number of ports for passing media through.

In the bipolar plate according to the application, at least one of the two half-sheets has a folded area adjacent to one of the ports, with flow channels being formed in the folded area.

The term “folded area” means that in the corresponding area the half sheet is present in two layers, with the two layers being connected to one another in one piece. The area connecting the two layers borders on one of the ports through which a medium, in particular a cooling medium, flows during operation of the electrochemical cell.

The folded area of the bipolar plate bordering one of the ports, in particular the coolant port, is formed by a folded section, which is also referred to as a folding grille without limiting generality, and by a non-folded section, which fits seamlessly into the surrounding area, at least partially embossed sections of the bipolar plate.

The so-called folding grille, which represents a second layer of the half-sheet of the bipolar plate, takes on the function of an insert, which provides channels through its shape at the same time acts as a supporting element. The mechanical support can play a role both in the manufacturing process of the bipolar plate, in particular when applying additional, non-metallic components, such as seals, as well as in the later operation of the electrochemical system, which is to be built using the bipolar plates, which will be discussed in more detail below will be.

According to a possible embodiment of the bipolar plate, a folded area providing flow channels is formed by each of the two half-sheets, the said areas of the half-sheets lying on top of each other. In particular, the folded areas can be designed to be mirror-symmetrical to a central plane of the bipolar plate.

The entire half sheets typically each have a rectangular basic shape. Those surface sections of the half-sheets on which the folded sections, i.e. folding grilles, rest, can be designed as flat partial surfaces of the half-sheets. The shape of the free flow cross sections through which operating or cooling medium flows is determined by the geometry of the folding grilles. Typically, numerous partial channels that run parallel to one another are formed by the folding grilles. In a manner that is easy to implement in terms of manufacturing technology, the area of the folded section is smaller than the area of the adjacent port.

The folded section, i.e. the folding grille, can be connected to the remaining half sheet in particular via two U-shaped bent webs. The two U-shaped webs can be arranged in particular on the two narrow sides of the overall rectangular folding grille. Configurations can also be realized in which the folding grille is connected to the remaining half-sheet via a larger number of strip-shaped, bent sections. The bent sections can also be used to influence the flow of the medium, for example to achieve turbulence effects.

Regardless of the type of one-piece connection between the folding grille and the remaining half sheet, the folding grille can, for example, have a trapezoidal profile in cross section and thus be designed in the manner of a trapezoidal sheet. Alternatively, rectangular or rounded profiles of the folded section can be considered. The folded gate does not necessarily have a uniform profile across its entire width. A variation of the profiling across the width of the folding grille can be carried out, for example, in order to set targeted changes in the fluidic and/or static properties transverse to the flow direction of the medium flowing from the port via the distribution field to the active field or in the opposite direction.

According to a possible further development, there is a sealing strip on the side of the half sheets facing away from the flow channels. This sealing strip is manufactured in particular by injection molding, i.e. sprayed onto the half-sheets that are already firmly connected to one another. In this process, the supporting function of the at least one folding grille plays an outstanding role in terms of the geometric precision that can be achieved and thus ultimately also the required sealing function of the non-metallic sealing strip.

• - Bereitstellung zweier jeweils eine Prägestruktur aufweisender Halbbleche, wobei in jedem der Halbbleche an ein Verteilerfeld angrenzende Ports zur Ein- und Ausleitung verschiedener Medien ausgebildet sind, und wobei zumindest in einem dieser Ports ein Klappgitter angeordnet ist, welches über Stege mit dem übrigen Halbblech verbunden ist, so dass in diesem Fertigungsstadium bei jedem Halbblech zwischen dem Klappgitter und dem Verteilerfeld eine schlitzförmige Öffnung gebildet ist,
• - Umklappen der Klappgitter um 180°, so dass diese auf dem Verteilerfeld des jeweiligen Halbblechs aufliegen,
• - Aufeinanderlegen der beiden Halbbleche, so dass sich die Klappgitter berühren und sowohl zwischen ebenen, den Verteilerfeldern zuzurechnenden Bereichen der Halbbleche und dem jeweils zugehörigen Klappgitter als auch zwischen den beiden Klappgittern Strömungskanäle und zugleich Stützstrukturen gebildet sind.

The process for producing the bipolar plate generally includes the following steps:

• - Provision of two half-sheets, each with an embossed structure, with ports adjacent to a distribution panel being formed in each of the half-sheets for the introduction and discharge of various media, and a folding grille being arranged in at least one of these ports, which is connected to the remaining half-sheet via webs , so that at this stage of production a slot-shaped opening is formed on each half sheet between the folding grille and the distribution panel,
• - Fold over the folding grilles by 180° so that they rest on the distribution panel of the respective half sheet,
• - Laying the two half-sheets on top of each other so that the folding grilles touch each other and flow channels and at the same time support structures are formed between flat areas of the half-sheets that are assigned to the distribution fields and the respective folding grille as well as between the two folding grilles.

After the half sheets have been placed on top of each other, they are finally connected to one another, in particular by welding. The optional, already mentioned spraying of seals represents the final manufacturing step.

• 1 ein teilfertiges Halbblech zur Herstellung einer Bipolarplatte,
• 2 einen Ausschnitt aus der Anordnung nach 1,
• 3 das Halbblech in fertiggestellter Form in einer Ansicht analog 2,
• 4 das fertiggestellte Halbblech in einer Ansicht analog 1
• 5 eine Draufsicht auf die aus zwei Halbblechen aufgebaute Bipolarplatte,
• 6 ein Detail der Bipolarplatte,
• 7 einen Ausschnitt aus der Anordnung nach 6,
• 8 ausschnittsweise die Bipolarplatte mit angespritzten Dichtungen.

An exemplary embodiment of the invention is explained in more detail below with reference to a drawing. Herein show:

• 1 a partially finished half sheet for producing a bipolar plate,
• 2 an excerpt from the arrangement 1 ,
• 3 the half sheet in finished form in an analogous view 2 ,
• 4 the finished half sheet in an analogous view 1
• 5 a top view of the bipolar plate made up of two half sheets,
• 6 a detail of the bipolar plate,
• 7 an excerpt from the arrangement 6 ,
• 8th A section of the bipolar plate with molded seals.

A bipolar plate, marked overall with the reference number 1, is constructed from two half-sheets 2, 3 lying one on top of the other and welded together and is intended for use in a fuel cell stack, not shown, that is, a stack of electrochemical cells. With regard to the basic function of the bipolar plate 1 in a fuel cell system, reference is made to the prior art cited at the beginning.

The bipolar plate 1 has various ports 4, 6 for the passage of operating media as well as ports 5 arranged between these ports 4, 6 for the passage of a cooling medium, in particular cooling water. An active field of the bipolar plate is designated 7. Between the active field 7 and the ports 4, 5, 6, distribution fields 8 are designed to distribute the various media flowing in or out.

The distribution of cooling water is examined in more detail below. The cooling water flows from port 5 into a structured flow space designated 9, which is formed between the half sheets 2, 3. On the one hand, a sufficiently large flow cross section must be provided in the flow space 9 for the cooling water; on the other hand, the half sheets 2, 3, which are embossed steel sheets, are to be supported against each other. The embossed structures of the half sheets 2, 3 are generally designated 10.

Before the half-sheets 2, 3 are assembled in their final form to form the bipolar plate 1, the half-sheets 2, 3 lie with one in the 1 and 2 recognizable partially finished form. In this form there is a so-called folding grille 11, which projects from the distribution panel 8 into the port 5 and is connected in one piece to the remaining half sheet 2, 3 via two webs 12. The folding grille 11 has a rectangular basic shape, with the webs 12 being formed onto the narrow sides of the folding grille 11. In the area of the folding grille 11, the embossed structure 10 is in the form of longitudinal grooves 13. The longitudinal grooves 13 are aligned parallel to the webs 12. This means that the longitudinal grooves 13 point towards the distribution field 8. Like, among other things 2 As can be seen, the longitudinal grooves 13 give a trapezoidal cross section of the embossed structure 10 of the folding grille 11. In the unfolded state of the folding grille 11, as in the 1 and 2 can be seen, there is a slot-shaped opening 14 between the folding grille 11 and the distribution panel 8, the width of which corresponds to the length of the webs 12.

In the exemplary embodiment, the webs 12 have a tapered shape, that is to say it becomes narrower towards the middle of the respective web 12. A straight line drawn through the narrowest area of the webs 12 marks the position of a tilt axis designated KA.

Before assembling the two half-sheets 2, 3, the folding grille 11 is folded onto that side of the half-sheet 2, 3 which is to be brought into contact with the other half-sheet 3, 2 during further assembly. In the arrangement according to the 3 and 4 This is the underside of the half-sheet 2. This produces a folded, i.e. double-layered area of the half-sheet 2, 3, designated 23.

As soon as the folding grille 11 is placed on the underside of the half sheet 2, that is to say the folded area 23 is formed, the webs 12 have an in 3 recognizable U-shape. At the same time, the full size of port 5 is created. The second half-sheet 3 is handled in the corresponding manner, so that after the half-sheets 2, 3 have been assembled, the ones in the 6 and 7 recognizable arrangement results. The half sheets 2, 3 are supported against each other by the embossed structures 10, which are in the form of the longitudinal grooves 13, which in the present case describe a trapezoidal profile.

Two different types of flow channels 15, 16 are formed here, namely inner flow channels 15 and further flow channels 16. The inner flow channels 15 are cut centrally through the central plane of the bipolar plate 1 and are limited exclusively by the two folding grilles 11 lying one on top of the other. In contrast, the further flow channels 16 lie above or below the central plane mentioned, each being delimited on the one hand by one of the folding grilles 11 and on the other hand by one of the half sheets 2, 3. All flow channels 15, 16 are aligned parallel to one another.

The folding grilles 11 folded inwards rest on a transition area 17, which is part of the distribution field 8. Through the transition region 17 there is a groove running transversely to the flow direction of the medium, i.e. coolant 18 of uneven height formed. In a central region 19 of the groove 18, this has a reduced depth in order to enable the folding grilles 11 to be placed between the half sheets 2, 3. In outer regions 20 of the groove 18, which adjoin the central region 19, on the other hand, the full depth of the groove 18 is given, so that the half sheets 2, 3 touch each other flatly in these regions 20.

Sealing strips 21, which are in 8th can be seen and overall result in a sealing arrangement 22, are applied by injection molding in such a way that they extend over all areas 19, 20 of the grooves 18. The non-uniform depth of the grooves 18 is also evident in the exemplary embodiment on the surfaces of the sealing arrangement 22 that are visible from the outside. The embossed structures 10 formed by the folding grids 11 and resting on one another ensure that no significant deformation of the half sheets 2, 3 occurs either when the sealing strips 21 are applied or during subsequent operation of the electrochemical cell having the bipolar plate 1.

Reference symbol list

1

Bipolar plate

2

Half sheet metal

3

Half sheet metal

4

Port for passing through an operating medium

5

Port for passing cooling water through

6

Port for passing through an operating medium

7

Active field

8th

distribution panel

9

Flow space for cooling water

10

Embossed structure

11

Folding grille, folded section

12

web

13

Longitudinal groove

14

slot-shaped opening

15

internal flow channel

16

another flow channel

17

Transition area

18

Nut

19

Middle area of the groove

20

outer area of the groove

21

sealing strip

22

Sealing arrangement

23

folded area

KA

Tilt axis

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 20110195332 A1 [0003]
• US 20110177429 A1 [0004]
• US 6410179 B1 [0004]
• US 20110033782 A1 [0005]
• US 20020172852 A1 [0005]
• DE 102014225160 A1 [0005]
• US 20150200404 A1 [0005]

Claims (10)

Bipolar plate (1) for a stack of electrochemical cells, with two half-sheets (2, 3) lying one on top of the other, through which an active field (7), a distribution field (8), and a number of ports (4, 5, 6) for the passage of media are formed, characterized in that at least one of the two half-sheets (2, 3) has a folded area (23) adjacent to one of the ports (4, 5, 6), flow channels (15, 16) being in the folded area (23). ) are trained. Bipolar plate (1). Claim 1 , characterized in that a folded region (23) providing flow channels (15, 16) is formed by each of the two half-sheets (2, 3), these regions (23) lying on top of each other. Bipolar plate (1). Claim 1 or 2 , characterized in that the flow channels (15, 16) are formed by a section (11) of the first half-sheet (2) which is folded over relative to the remaining half-sheet (2), said section (11) resting on the second half-sheet (3). . Bipolar plate (1). Claim 3 , characterized in that the area of the folded section (11) is smaller than the area of the adjacent port (5). Bipolar plate (1). Claim 4 , characterized in that the folded section (11) is connected to the remaining half sheet (2, 3) via two U-shaped bent webs (12). Bipolar plate (1) according to one of the Claims 3 until 5 , characterized in that the folded section (11) is profiled trapezoidally. Bipolar plate (1) according to one of the Claims 2 until 6 , characterized in that there is a sealing strip (21) on the side of the half sheets (2, 3) facing away from the flow channels (15, 16). Method for producing a bipolar plate (1), with the following steps: - Provision of two half-sheets (2, 3), each having an embossed structure (10), ports (4, 5, 6) adjacent to a distribution panel (8) being formed in each of the half-sheets (2, 3), and at least in one A folding grille (11) is arranged in these ports (4, 5, 6), which is connected to the remaining half sheet (2, 3) via webs (12), so that for each half sheet (2, 3) between the folding grille (11 ) and the distribution field (8) a slot-shaped opening (14) is formed, - Fold the folding grilles (11) by 180° so that they rest on the distribution panel (8) of the respective half sheet (2, 3), - Laying the two half-sheets (2, 3) on top of each other so that the folding grilles (11) touch each other and between flat transition areas (17) of the half-sheets (2, 3) that are assigned to the distribution fields (8) and the respective folding grille (11) as well as between the two folding grilles (11) flow channels (15, 16) and at the same time support structures are formed. Procedure according to Claim 8 , characterized in that sealing strips (21) are applied to the outside of the flat transition areas (17) of the distribution panels (8). Procedure according to Claim 9 , characterized in that the sealing strips (21) are produced by injection molding after joining the two half sheets (2, 3).

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