DE102008028358A1 - Separator plate i.e. bipolar plate, for fuel cell, has metallic core comprising plastic coating with electrically conductive plastic material and guiding structures i.e. pipes, for guiding coolant - Google Patents

Abstract

The separator plate (10) has a metallic core (12) comprising a plastic coating (16) with an electrically conductive plastic material. The plastic material is a mixture of thermoplastics, thermosetting polymers and carbon. The metallic core comprises guiding structures i.e. pipes (14.1, 14.2), for guiding coolant. The pipes comprise inlet openings (34.1, 34.2) and outlet openings (36.1, 36.2), where the inlet openings and the outlet openings discharge into a circular edge (22) of the separator plate. Independent claims are also included for the following: (1) a galvanic cell comprising electrolytes (2) a method for manufacturing a separator plate.

Description

The The invention relates to a separator plate for a galvanic Cell, wherein the separator plate comprises a metal core. According to one second aspect, the invention relates to a method of manufacturing a separator plate for a galvanic element.

separator are, for example, unipolar plates or bipolar plates and separate in galvanic cells a container filled with electrolyte from an environment of the galvanic cell.

From the CA 2 538 961 a bipolar plate is known in the interior of a grooved plate is arranged so that parallel channels are formed. Through the channels, a cooling medium can be sent to cool the separator plate.

From the DE 10 2005 046 795 A1 is a coolable bipolar plate is known in which a plurality of corrugated sheets are mutually rotated from each other separated by a partition plate, wherein the corrugated sheets form cooling channels, which are designed so that the flow rates have a predetermined ratio to each other.

adversely The known bipolar plates are expensive are in production. They also build relatively thick, so that compact Fuel cells can only be produced badly.

Of the Invention is based on the object, the production of Separatorplatten to facilitate.

The Invention solves the problem by a generic Separator plate, in which the metal core with an electrically conductive Plastic material is sheathed. According to one second aspect, the invention solves the problem by Method for producing a separator plate with the steps inserting a metal core into a tool and sheathing the metal core with electrically conductive plastic material, so that a separator plate is formed.

Advantageous to the invention is that thin-build separator plates to be obtained. These allow the construction of thinner galvanic cells, in particular thin fuel cells.

It Another advantage is that separator plates by means of the invention easy to manufacture. For example, the sheathing by Overmolding or hot stamping. It deals this involves cost-effective mass procedures.

One Another advantage is that Separatorplatten according to the Invention are particularly stable. Due to the fact that the metal core with the electrically conductive plastic material sheathed both are intimately connected by vibrations, Shearing and / or torsional forces as well as surface forces can hardly be separated. This is especially beneficial if the separator plates are used in a fuel cell. In this case, the fuel cell is useless if only one the bipolar plates fail. Characterized in that the separator plates according to the Invention are particularly robust, the probability of failure for such a fuel cell significantly lower than in conventional fuel cells.

in the The scope of the present description is under a metal core understood any metallic component in an interior of the separator. It is possible, but not necessary, that the metal core completely made of metal. For example, the Metal core have an air-filled cavity or be filled with other material.

Under the feature that the metal core with an electrically conductive Plastic material is covered, is understood in particular, that the metal core, if the separator plate in a galvanic Element is arranged completely through the plastic material is separated from an electrolyte. In particular, the metal core then sheathed with the plastic material when the metal core in Essentially completely covered with plastic material is. But it is possible that the metal core from the plastic sheath runs out. This is especially the case when the metal core as a cooling tube for a cooling liquid is trained.

separator should be particularly good electrically conductive, so that the large currents flowing in a fuel cell opposes the lowest possible ohmic resistance becomes. Therefore, the use of electrically conductive Plastic material whose conductivity is usually clear smaller than that of metal, at first glance not effective. However, it has been found that by the overmolding with electrically conductive plastic material in purchase taking increased ohmic resistance is outweighed by the advantage that the separator plates according to the invention are particularly can be manufactured inexpensively.

It has proven to be advantageous when the specific electric Conductivity of the plastic material above 10 S / cm, especially above 40 S / cm.

According to a preferred embodiment, the metal core is overmolded or embossed with the conductive plastic material. That leads to a Minimum material thickness of the plastic material always exceeds a predetermined threshold of, for example, 0.5 mm.

Prefers the plastic material is a mixture of at least one thermoplastic and / or a thermosetting plastic and at least one plastic modification.

For example is the carbon modification carbon black, graphite, graphene carbon tubes or a mixture of two or three of these components. It has it turned out that there is such a particularly high specific electrical Conductivity can be achieved. Such plastic material is also particularly inexpensive to produce.

Prefers is in the plastic material on at least one surface, in the installation position of the separator plate facing an electrolyte is introduced, a Gasleitstruktur. If the separator plate for example, as a bipolar or unipolar plate in a fuel cell is used, takes place on the surface of the separator plate a chemical reaction takes place. This must be either hydrogen or Oxygen supplied constantly and with the electrolyte be brought into contact. The gas guiding structure is formed to facilitate the introduction of these gases into the electrolyte. It is advantageous that the Gasleitstruktur particularly easy in the Surface can be introduced. For example namely the separator plate by hot stamping produced. In this case, a tool can be used whose inner surface has a contour which is a negative the gas guide structure corresponds. Alternatively, it is also possible the Gasleitstruktur for example by machining or forming in bring in the surface, but this causes in the Usually a higher production cost.

The Separator plate can be cooled very easily, if the metal core at least one conductive structure, in particular a Tube, for conducting a cooling medium comprises. In this case The metal core fulfills a double task. On the one hand It causes the electrical resistance for a flow of current from one side of the separator plate to the other is kept small, on the other hand, resulting in the Separatorplatte Heat can be easily dissipated, reducing the life and Increases the efficiency of a fuel cell, in which the separator plate is installed.

Especially Preferably, the tube has an inflow opening and an outflow opening, wherein the inflow opening or the outflow opening in a circumferential Open the edge of the separator plate. That way that can Cooling medium are particularly easy to be supplied.

In a galvanic element according to the invention, in particular a fuel cell according to the invention, For example, the metal core is preferred with a current drain device for dissipating electrical current, that of galvanic Element was generated, electrically connected.

Prefers is the metal core in the form of the conductive structure for conducting the cooling medium with a corresponding unit for supplying coolant connected.

One Method according to the invention preferably comprises the steps of inserting a first plastic pre-body in a sub-tool or lower tool of a tool, an insert a metal core in the tool, so that the metal core and the first plastic preform flat to each other lie, an insertion of a second plastic pre-body in the tool, leaving the second plastic preform and the metal core lie flat against each other and one Pressing the first plastic pre-body, the metal core and the second plastic preform under heat, so that these make some connections. The lower tool can be arranged below a second sub-tool or upper tool, but that is not necessary. For example, this is the first subtool arranged spatially next to the second part tool, so that both are, for example, the same or similar Height can be located.

in the The invention will be described below with reference to exemplary embodiments with reference to the accompanying drawings by way of example explained in more detail. It shows

1 a schematic three-dimensional view of a separator plate according to the invention,

2a . 2 B alternative embodiments of a separator plate according to the invention,

3a . 3b further alternative embodiments of a separator plate according to the invention,

4 a further alternative embodiment of a separator according to the invention. The

5 to 10 show cross sections of metal cores for a separator plate according to the invention.

1 shows a separator plate 10 in the form of a bipolar plate with a metal core 12 , in the present case through a first pipe 14.1 and a second tube 14.2 is formed. The metal core 12 is with a plastic jacket 16 made of plastic material jacketed.

The Plastic material consists for example of 14 wt .-% polypropylene and 86% by weight of a graphite / carbon black mixture. It is also possible to provide more polypropylene, for example 22.5%, the remainder being formed by the graphite / carbon black mixture is.

On a first surface 18 the separator plate 10 a not shown Gasleitstruktur is introduced. This Gasleitstruktur comprises a plurality of small, interconnected channels, in which gas from a likewise not shown gas supply to an interior of the first surface 18 to be directed. As a result, the gas, for example hydrogen or oxygen, is brought into intimate contact with an electrolyte which, in the installed position, is in contact with the first surface 18 stands.

In the same way, a gas guiding structure is in a second surface 20 introduced parallel to the first surface 18 runs. The first surface 18 and the second surface 20 have a distance D from each other, which is a thickness of the separator plate 18 represents and is for example more than 0.5 mm. In particular, the thickness D is smaller than 2.5 cm.

The metal core 12 is so in the plastic jacket 16 arranged that he has a minimum distance d _min from the first surface 18 which has a minimum distance to the second surface 20 corresponds and, for example, less than 5 mm. Although the plastic material may have a specific electrical conductivity of more than 50 S / cm, it is nevertheless advantageous to provide the smallest possible minimum distance d _min since the separator plate is then particularly thin and light. In order to achieve a sufficient stability of the separator plate, the minimum distance d _{min is} usually chosen to be greater than 0.5 mm.

The pipes 14.1 . 14.2 occur through a peripheral edge 22 from the separator plate 10 off and are in installation position of Separatorplatte 10 connected to a connection to a cooling device through which cooling medium is circulated therethrough.

2a shows a second embodiment of a separator according to the invention 10 in which the metal core 12 through a variety of pipes 14.1 . 14.2 , ... is formed. In the following, a reference number without counting suffix designates the object as such. The pipes 14 kick through the edge 22 in a first edge section 24.1 in the rectangular plastic jacket 16 and leave this by the edge 22 in a first edge section 24.1 opposite edge section 24.3 ,

The pipes 14 are with their respective inflow openings with a supply line 26 connected by the arrows indicated by a cooling medium 28 , For example, water in the pipes 14 is directed. With their outflow openings are the pipes 14 with a derivative 30 connected, via which the cooling medium 28 is deducted. The supply line 26 and the derivative 30 may also according to an alternative embodiment of the plastic sheath 16 be surrounded. For mounting in a fuel cell, the separator plate comprises 10 gas supply lines 32.1 . 32.2 . 32.3 . 32.4 for supplying the reactants in the form of hydrogen and oxygen.

2 B shows an alternative separator plate, in which the supply line 26 and the derivative 30 in a plastic jacket 16 run. The cooling medium 28 enters through two inlet openings 34.1 . 34.2 through the opposite edge sections 24.2 . 24.4 through the edge 22 one and through outlet openings 36.1 . 36.2 also by the edge 22 from the plastic jacket 16 out again.

3a shows an alternative embodiment of a separator plate 10 in which the pipes 14.1 . 14.2 in a twin arrangement meandering through the plastic jacket 16 are guided.

3b shows a separator plate 10 in which a pipe 14 in the form of a spiral through the plastic jacket 16 is guided.

4 shows a separator plate 10 in which a variety of pipes 14.1 . 14.2 , ... snake-shaped in a plastic jacket 16 are arranged.

5 shows a possible cross section of a pipe 14 , the part of the metal core 12 is (cf. 1 ). The pipe 14 has a Φ-shaped cross-section with a top surface 38 and parallel to this foot area 40 over a footbridge 42 connected to each other. In the dock 42 is a channel 44 formed with, for example, circular cross-section. The pipe 14 is as shown in the previous figures, in the plastic jacket 16 arranged.

6 shows an alternative form for a pipe 14 in the form of a cross, in the center of which is the canal 44 is arranged.

7 shows a further cross section, which is particularly suitable for a unipolar plate. The channel 44 , which is cylinder jacket-shaped, borders on one side to a cuboidal plate, which forms the foot surface 40 formed. On the opposite side is the canal 44 connected with a wedge-shaped structure, on which the head surface 38 is trained.

8th shows a further embodiment of a tube 14 which has a cross section in the form of a regular hexagon.

9 represents an alternative tube 14 whose cross-section is an equilateral hexagon.

10 shows another tube 14 whose cross-section is formed by two equilateral triangles connected at their tips.

The separator plate according to the invention is produced, for example, by an in 1 indicated first plastic preform 46 is placed in a hot stamping mold. On the first plastic preform 46 becomes the metal core 12 hung up. It can in the plastic preform 46 already recesses, such as gutters, be provided in the pipes 14 be inserted.

The following is the plastic preform 46 and the pipes 14 with a second plastic preform 48 covered. An existing from an upper tool and a lower tool hot stamping tool is then so on the two plastic preform 46 . 48 delivered that these also partially melt and with each other and with the metal core 12 connect.

There is a particular difficulty in ensuring that the metal core 12 when connecting with the plastic pre-bodies 46 . 48 does not fall below a predetermined threshold value for the minimum distance d _min . The necessary process technology has only recently become available.

To the Avoiding trapped air can affect the shape before joining be evacuated by means of pressure and heat.

The plastic preform 46 . 48 consist for example of the following material: 14 wt .-% polypropylene and 86 wt .-% of a graphite / carbon black mixture. It is also possible to provide more polypropylene, for example 22.5%, the remainder being formed by the graphite / carbon black mixture.

10

separator

12

metal core

14

pipe

16

Plastic sheath

18

first surface

20

second surface

22

edge

24

edge section

26

supply

28

cooling medium

30

derivation

32

gas supply

34

inlet openings

36

outlet opening

38

head face

40

foot surface

42

web

44

channel

46

first Plastic preform

48

second Plastic preform

D

thickness

d _mjn

minimal distance

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• CA 2538961 [0003]
• DE 102005046795 A1 [0004]

Claims (14)

Separator plate for a galvanic element with a metal core ( 12 ), characterized in that the metal core ( 12 ) is coated with an electrically conductive plastic material. Separator plate according to claim 1, characterized in that the metal core ( 12 ) is overmolded or embossed with the conductive plastic material. Separator plate according to one of the preceding claims, characterized in that the plastic material is a mixture of at least one thermoplastic and / or a thermoset and at least one carbon modification. Separator plate according to one of the preceding claims, characterized in that in the plastic material on at least one surface ( 18 . 20 ), which in the installation position of the separator plate ( 10 ) facing an electrolyte, a Gasleitstruktur is introduced. Separator plate according to one of the preceding claims, characterized in that the metal core ( 12 ) at least one guide structure, in particular a tube ( 14 ), for conducting a cooling medium ( 28 ). Separator plate according to claim 5, characterized in that - the at least one tube ( 14 ) an inflow opening ( 34 ) and an outflow opening ( 36 ), the inlet opening ( 34 ) and / or outflow opening ( 36 ) in a peripheral edge ( 22 ) of the separator plate ( 10 ). Separator plate according to one of the preceding claims, characterized in that it is a bipolar plate. Galvanic cell, in particular fuel cell, with - an electrolyte, - a separator plate according to one of claims 5 or 6 and - a cooling device for charging the conductive structure ( 14 ) with a cooling medium. Galvanic cell according to claim 8, characterized in that the metal core ( 12 ) is electrically connected to a current drain device for dissipating electric power generated by the galvanic cell. Method for producing a separator plate, comprising the steps of: - inserting a metal core ( 12 ) into a tool and - sheathing the metal core ( 12 ) with electrically conductive plastic material, so that a separator plate is formed. Method according to claim 10, characterized in that that wrapping comprises overmolding. Method according to claim 10 or 11, characterized that wrapping is a hot stamping. A method according to claim 12, characterized in that the hot stamping comprises the following steps: - inserting a first plastic preform ( 46 ) in a lower tool of the tool, - inserting the metal core ( 12 ) in the tool so that the metal core ( 12 ) and the first plastic preform ( 46 ) lie flat against each other, - insert a second plastic preform ( 48 ) in the tool, so that the second plastic preform ( 48 ) and the metal core ( 12 ) lie flat against one another, and - pressing the first plastic preform ( 46 ), the metal core ( 12 ) and the second plastic preform ( 48 ) under heat, so that they form an intimate connection. A method according to claim 11 or 13, characterized through the step: - Evacuate before pressing of the tool.