FLOW FIELD PLATE AND METHOD FOR PRODUCING SAME

Abstract

The invention relates to a flow field plate (1) for a fuel cell, consisting of a synthetic resin (A-B) with fillers that comprise at least graphite (C) and/or carbon black. The flow field plate (1) according to the invention is characterized in that a polyurethane resin (PUR) is used as the synthetic resin (A-B).

Claims

1. A flow field plate for a fuel cell made of a synthetic resin with fillers which comprises at least graphite and/or carbon black, wherein a polyurethane resin is used as the synthetic resin. the polyurethane resin (A-B) is produced from two liquid starting components (A, B), one of which comprises isocyanate (B) or polyisocyanate and/or one of which comprises polyols (A), and both starting components (A, B) are provided with graphite (C) and/or carbon black as a filler.

2. (canceled)

3. (canceled)

4. (canceled)

5. The flow field plate according to claim 1, wherein the fillers make up more than 60 to 70% by volume, preferably approx. 80% by volume, of the finished component.

6. The flow field plate according to claim 1, wherein pure, preferably synthetic, graphite and/or carbon black are/is used as the sole filler.

7. A method for producing a flow field plate for a fuel cell made of a synthetic resin with a filler, wherein at least two starting components are cured to form the synthetic resin, wherein the starting components used are those that form a polyurethane resin and being mixed in liquid form and then cured at least temporarily in a tool that generates the structure of the flow field plate under the action of temperature, and the starting components (A, B) used are polyols (A) and isocyanate (B), both of which are provided with graphite (C) and/or carbon black as filler prior to mixing.

8. (canceled)

9. The method according to claim 7, wherein a temperature of approx. 50 to 60° C. is specified at least to start curing.

10. The method according to claim 7, wherein the starting components together with the filler are pressed into the tool and/or held in it at least temporarily under pressure.

11. The flow field plate according to claim 2, wherein the fillers make up more than 60 to 70% by volume, preferably approx. 80% by volume, of the finished component.

12. The flow field plate according to claim 3, wherein the fillers make up more than 60 to 70% by volume, preferably approx. 80% by volume, of the finished component.

13. The flow field plate according to claim 4, wherein the fillers make up more than 60 to 70% by volume, preferably approx. 80% by volume, of the finished component.

14. The flow field plate according to claim 5, wherein pure, preferably synthetic, graphite and/or carbon black are/is used as the sole filler.

15. The method according to claim 9, wherein the starting components together with the filler are pressed into the tool and/or held in it at least temporarily under pressure.

Description

[0015] Further advantageous configurations of the flow field plate according to the invention and the method for its production also result from the exemplary embodiments, which are explained in more detail below with reference to the figures.

[0016] FIG. 1 shows a schematic view of a flow field plate in an exemplary geometric configuration comparable to the prior art; and

[0017] FIG. 2 shows a schematic representation of the method according to the invention.

[0018] FIG. 1 shows the plan view of a flow field plate labeled 1, for example the anode side of a flow field plate 1. Flow field plate 1 has on both sides, the so-called headers, several openings 2 to 7, which are used for the supply and removal of media. The exemplary embodiment shown here, shows the plan view on the surface of flow field plate 1 which faces the anode side of an adjacent single cell of a fuel cell stack, which is not shown in its entirety. It has, for example, the opening labeled 2 at the top right, which, together with comparable openings in adjacent flow field plates 1, forms a supply channel for hydrogen. Hydrogen then flows through said opening 2, which forms part of the supply channel, to each of the flow field plates 1 and into a collection or distribution area 11 of a flow field labeled 12 in its entirety via connecting channels labeled 10. Distribution area 11 has an open structure, for example with the nubs indicated here, in order to enable a transverse distribution of hydrogen. A channel structure 13 is located in the further course of the flow field 12 in the direction of flow. The gases are distributed to the anode side of the individual cell via said channel structure 13 having parallel channels that are closed to one another. The collection or distribution area 11 helps ensure that the flow through all the channels of channel structure 13 is as uniform as possible. After flowing through the channels of channel structure 13, the residual gas, mixed with the product water generated in the fuel cell, reaches a collection area labeled 14 and comparable to distribution area 11, in which the gas/liquid mixture accumulates. It then flows via connecting channels 15 on the outflow side into the opening labeled 5 which, together with further analogous openings in adjacent flow field plates 1, forms a discharge channel 16.

[0019] The structure for the cathode side of the adjacent single cell on the opposite side of flow field plate 1 looks substantially the same. The air or the oxygen is supplied, for example, via opening 4 and correspondingly discharged via opening 7. Openings 3 and 6, which are somewhat larger in cross section in most structures, are provided for the supply and removal of liquid cooling medium, for example cooling water. It is often the case that flow field plates 1 are formed from two partial plates, which are connected to one another at their rear sides. They then form further channels between their rear sides, through which cooling liquid can flow via openings 3 and 6. All of this is known to the person skilled in the art so that it does not need to be discussed further.

[0020] The special feature of flow field plate 1 is its material. Said flow field plate 1 consists of a polyurethane resin (PUR), which is produced with an electrically conductive filler in the form of graphite and/or carbon black in the manner described in more detail below. Such a polyurethane resin system for flow field plate 1 provides extraordinary flexibility and high strength with good functionality. The production method enables further energetic and process-related advantages compared to the synthetic resin-bonded systems according to the prior art.

[0021] The production method is indicated schematically in the illustration of FIG. 2. A first starting component A, which is indicated here by way of example in a container 16, is provided with graphite C in an indicated container labeled 17. The two substances are appropriately mixed in container 18 so that there is a mixture A-C. Starting component A can preferably be polyols, while the filler in the form of graphite C is synthetic graphite with a correspondingly small particle size on the order of a few microns. Graphite C can be distributed very homogeneously and uniformly in the liquid starting component A.

[0022] A similar procedure is shown on the right-hand side of FIG. 2. A starting component labeled B in a container 19 is also mixed with graphite C from a container 20 so that there is a mixture B-C made of second starting component B and graphite C in container 21. The same features and parameters apply to the graphite here as were previously described in the left-hand part of the figure when mixing the graphite C with first starting component A. Second starting component B, which is also in liquid form and is mixed with graphite C, is isocyanate. The starting components A-C and B-C, which have each been mixed with graphite C and are still liquid, are then mixed with one another so that there is a component mixture A-B-C in the container labeled 22, wherein, due to the fact that graphite C has been premixed already with the individual liquid starting components A, B, an extremely homogeneous mixture can be achieved.

[0023] The proportion of graphite in this mixture is approx. 80% by volume. The uniform and homogeneous distribution ensures later on an even and homogeneous electrical conductivity of flow field plate 1, which is to be produced from mixture A-B-C.

[0024] As indicated by arrow 23, said mixture A-B-C is then added into a tool 24 having a structure which is designed as a negative of the structure desired in flow field plate 1. At a temperature T of approx. 50 to 60° C. and, optionally, at a pressure P above atmospheric pressure, mixture A-B-C then cures in tool 24 to form flow field plate 1, with the entire curing process not necessarily having to take place in tool 24, but, optionally, only part of the same can take place there. The structure is then extremely stable, has low porosity and relatively high flexibility, so that flow field plate 1 can be out-of-tool and without further method steps such as tempering or the like. As already mentioned above, different types of tools 24 are possible, so that it is clear to the person skilled in the art that tool 24 indicated in FIG. 2, which is shown here by way of example as an open casting mold, only represents one possible exemplary embodiment.