Method for manufacturing bipolar plates

Abstract

A method for manufacturing a bipolar plate (2) for use in a fuel cell includes the following steps: providing (100) a bipolar plate (2') made of a composite material (8), the composite material comprising a conductive layer material (6) and a non-conductive layer material (4); selectively removing (200) portions of the non-conductive layer material (4) from the composite material (8) by means of a first material removal method to expose some areas of the conductive layer material (6) on the surface (O) of the bipolar plate (2'); applying (300) a functional layer (10) to the surface (O) of the bipolar plate (2') by means of a coating method to functionalize the surface (O) of the bipolar plate (2'); and selectively removing (400) portions of the functional layer (10) by means of a second material removal method to expose some areas of the conductive layer material (6).

Description

Technical Field

[0001] This invention is based on a method for manufacturing bipolar plates and a bipolar plate preferably manufactured by this method. Furthermore, this invention relates to a fuel cell having a plurality of bipolar plates of this type. Background Technology

[0002] A fuel cell is an electrochemical energy converter in which reactant gases, such as hydrogen and oxygen, are converted into water, electricity, and heat. In this case, the reactant gases are separated via a polymer membrane, which provides the necessary isolation. Typically, a fuel cell has a symmetrical structure in which a catalyst layer and a gas distribution layer are arranged on either side after the polymer membrane, and bipolar plates are respectively connected to the catalyst layer and the gas distribution layer. The bipolar plates arranged within the fuel cell perform multiple functions. They are used for electrically connecting the cell cells, inputting and distributing the reactant gases, and inputting and distributing the coolant.

[0003] For reasons of weight, cost and durability, bipolar plates made of composite materials have now been constructed, in which conductive particles are processed into the plastic material.

[0004] On the downside, because the conductive particles are coated with plastic, the material's conductivity and surface wettability are reduced, which ultimately hinders mass transport within the fuel cell and thus reduces the fuel cell's performance. Summary of the Invention

[0005] The subject matter of this invention, according to a first aspect, is a method having the features of a separate method claim, and according to a second aspect, is a bipolar plate having the features of a separate device claim. According to a third aspect, the invention also relates to a fuel cell having a plurality of bipolar plates having the features of a separate device claim. Further features and details of the invention are derived from the corresponding dependent claims, the description, and the drawings. The features and details described herein in conjunction with the method according to the invention are of course also applicable to the bipolar plate according to the invention or the fuel cell according to the invention, and vice versa, so that disclosures relating to individual aspects of the invention are always mutually referenced or may be mutually referenced.

[0006] The method according to the invention for manufacturing a bipolar plate for use in a fuel cell comprises, in this case, the following steps: providing a bipolar plate made of a composite material, the composite material comprising a conductive layer material and a non-conductive layer material; selectively removing portions of the non-conductive layer material from the composite material by means of a first material removal method to expose portions of the conductive layer material on the surface of the bipolar plate; applying a functional layer to the surface of the bipolar plate by means of a coating method to functionalize the surface of the bipolar plate; and selectively removing portions of the functional layer by means of a second material removal method to expose portions of the conductive layer material.

[0007] The method for manufacturing bipolar plates according to the invention is preferably used to improve the conductivity of bipolar plates made of composite materials, especially plastic-based bipolar plates, and to reduce the contact resistance between the bipolar plates and other components when the bipolar plates are arranged within a fuel cell. Advantageously, durable hydrophilicity of the bipolar plates made of composite materials can be achieved in this case, wherein mass transport, particularly of process gases and reactive water, is supported to enter or leave the composite material by using a (preferably porous) coating. Surface functionalization can be performed, particularly within a single device, by using non-layering and layering (plasma) processes, allowing for the process steps of cleaning the surface, exposing conductive particles, activating the composite material surface, and coating the composite material surface for hydrophilicity in a single process. Furthermore, the dimensions of the bipolar plates can be maintained, or changed only to a minimal extent, by removing and subsequently applying materials (preferably in the nanometer to micrometer range).

[0008] The bipolar plates processed according to the method of the invention are preferably used in fuel cells or fuel cell systems of motor vehicles. Similarly, their use in other fuel cell-powered vehicles or stationary systems is also conceivable. Needless to say, the bipolar plates according to the invention can also be used in electrolysis devices. Preferably, according to the invention, the functional layer can be understood as a layer that performs a specific task or function, such as accelerating or ensuring mass transport or similar functions.

[0009] Within the framework of this invention, it has been discovered that by using a bipolar plate made of composite material and by selectively removing the plastic surface, near-surface conductive particles can be exposed in a simple and low-cost manner, and the plastic surface can be activated. Furthermore, it has also been found that by applying a thin, hydrophilic, porous coating that adheres well to the activated adhesive but poorly to the conductive filler, it is possible to easily peel off the poorly adhered layer portion onto the conductive filler.

[0010] In terms of precisely and controllably selectively removing non-conductive layer regions of the composite material from the surface of the bipolar plate, it is particularly advantageous according to the invention that the first material removal method for selectively removing portions of the non-conductive layer material is constructed in the form of an etching method, preferably a plasma etching method. The plasma etching method can be constructed in the form of a dry etching method, a wet etching method, or a combination of both. By selectively removing the non-conductive layer regions of the composite material from the surface of the bipolar plate to expose the conductive layer regions of the composite material, the surface energy of the composite material can be increased in particular, making temporary hydrophilicity possible.

[0011] To controllably apply a thin functional layer to a substrate while selectively adjusting layer characteristics, the present invention advantageously provides a coating method for applying the functional layer to the surface of a bipolar plate, configured as a vacuum coating method, preferably a PVD method or a CVD method, particularly a plasma-based PVD or CVD method. By using a plasma-supported method, improved layer quality can be achieved, in particular, through improved adhesion, more selective deposition, and less contamination. Plasma-based PVD methods can be configured, for example, as magnetron sputtering or reactive sputtering. Plasma-based CVD methods can also be configured as LPCVD or PE-CVD methods. Alternatively, a spraying method can also be used to apply the functional layer.

[0012] Regarding the stable connection of the functional layer in the desired region, the invention further includes: drying the applied functional layer before selectively removing certain portions thereof, wherein drying of the applied functional layer is preferably achieved by introducing an airflow and / or by irradiation with a radiation source. The introduced airflow is preferably configured as a hot airflow. The radiation source is also preferably configured as an IR radiation source for emitting electromagnetic radiation in the infrared frequency range.

[0013] Within the framework of simple, low-cost, and efficient selective removal of the functional layer, a second material removal method for selectively removing portions of the functional layer can also be advantageously configured as a mechanical removal method, preferably using a scraper and / or brush and / or compressed air. Due to the varying degrees of adhesion of the functional layer to conductive and non-conductive regions, the functional layer can be easily removed from the conductive regions of the functional layer via the mechanical removal method, while the functional layer remains on the non-conductive regions.

[0014] Similarly, the subject matter of the invention also includes a bipolar plate for use in a fuel cell, preferably manufactured by processing a bipolar plate made of a composite material, particularly according to one of the methods described above, the composite material comprising conductive and non-conductive layer materials. In this case, the bipolar plate according to the invention comprises a first layer having a non-conductive layer material, and a second layer disposed on the first layer having conductive and functional layer materials, wherein the functional layer materials are disposed between the conductive layer materials. Therefore, the bipolar plate according to the invention exhibits the same advantages as those already described in detail regarding the method according to the invention.

[0015] In the framework of manufacturing stable and insensitive bipolar plates at low cost, the present invention can advantageously provide that the non-conductive layer material is constructed in the form of a plastic, optionally in the form of a thermoplastic or thermosetting plastic, particularly in the form of polyethylene (PE) or polypropylene (PP) as thermoplastics or in the form of phenolic resin or epoxy resin as thermosetting plastics. The use of this type of plastic material further ensures a weight-optimized implementation.

[0016] Within the framework of manufacturing weight-optimized bipolar plates for efficient charge transport at low cost, the present invention advantageously provides that the conductive layer material is constructed in the form of a carbon-containing material, preferably graphite. Instead of graphite, the carbon-containing material can also be constructed in the form of graphene, carbon fibers, or similar materials.

[0017] To functionalize the non-conductive surface regions of the bipolar plate according to the invention, the functional layer material can advantageously comprise a silicon-containing compound, preferably a siloxane and / or a silane and / or an aminosilane and / or an alkanithi. Furthermore, self-assembled monolayers (SAMs) can be used, particularly for surfaces that are specifically designed for functionalization. In this case, the functionalization should especially ensure a layer that is not only porous but also hydrophilic to optimize gas distribution and drainage.

[0018] Within the framework of specifically controlling the performance of the bipolar plate according to the invention, the invention can also advantageously provide that the second layer has a layer thickness of <100 μm, preferably <10 μm, and especially <1 μm.

[0019] Similarly, the subject matter of the invention also includes a fuel cell having a plurality of the aforementioned bipolar plates. Therefore, the fuel cell according to the invention exhibits the same advantages as those already described in detail regarding the method according to the invention or the bipolar plates according to the invention.

[0020] Other advantages, features, and details of the invention will become apparent from the following description, in which embodiments of the invention are described in detail with reference to the accompanying drawings. Here, the features mentioned in the claims and description may be substantial to the invention individually or in any combination. Attached Figure Description

[0021] Figure 1 : Schematic diagrams of the various steps of a method for manufacturing a bipolar plate for use in a fuel cell according to the present invention, and Figure 2 : A schematic diagram of a bipolar plate for use in a fuel cell according to the present invention. Detailed Implementation

[0022] Figure 1 A schematic diagram illustrating the various steps of a method according to the invention for manufacturing a bipolar plate 2 for use in a fuel cell.

[0023] For example, according to Figure 1 As can be seen, the method according to the present invention includes the steps of: providing a bipolar plate 2' made of a composite material 8, the composite material having a conductive layer material 6 and a non-conductive layer material 4; selectively removing 200 portions of the non-conductive layer material 4 from the composite material 8 by means of a first material removal method to expose some areas of the conductive layer material 6 on the surface O of the bipolar plate 2'; applying 300 functional layer 10 having a functional layer material 10' to the surface O of the bipolar plate 2' by means of a coating method to functionalize the surface O of the bipolar plate 2'; and selectively removing 400 portions of the functional layer 10 by means of a second material removal method to expose some areas of the conductive layer material 6.

[0024] A first material removal method for selectively removing portions of the 200 non-conductive layer material 4 can be constructed, for example, in the form of an etching method, preferably in the form of a plasma etching method.

[0025] The coating method for applying the 300 functional layer 10 on the surface O of the bipolar plate 2' can also be constructed in the form of a vacuum coating method, preferably a PVD method or a CVD method.

[0026] The second material removal method for selectively removing some portions of the 400 functional layer 10 can also preferably be constructed in the form of a mechanical removal method, such as using a scraper and / or a brush and / or compressed air.

[0027] Figure 2 A schematic diagram of a bipolar plate 2 for use in a fuel cell according to the present invention is shown.

[0028] For example, according to Figure 2As can be seen, the bipolar plate 2 includes a first layer 12 having a non-conductive layer material 4 and a second layer 14 having a conductive layer material 6 and a functional layer material 10' disposed on the first layer 12, wherein the functional layer material 10' is disposed between the conductive layer materials 6.

[0029] The non-conductive layer material 4 can be constructed, for example, in the form of a plastic, optionally in the form of a thermoplastic (polyethylene or polypropylene) or a thermosetting plastic (phenolic resin or epoxy resin).

[0030] The conductive layer material 6 can also be constructed in the form of a carbon-containing material, preferably in the form of graphite.

[0031] The functional layer material 10' may further include silicon-containing compounds, preferably siloxanes and / or silanes and / or aminosilanes and / or alkylthiols.

Claims

1. A method for manufacturing a bipolar plate (2) for use in a fuel cell, comprising the following steps: - Provide (100) a bipolar plate (2') made of composite material (8), said composite material comprising a conductive layer material (6) and a non-conductive layer material (4). - Using a first material removal method, some portions of the non-conductive layer material (4) are selectively removed (200) from the composite material (8) to expose some areas of the conductive layer material (6) on the surface (O) of the bipolar plate (2'). - By means of a coating method, a functional layer (10) (300) is applied to the surface (O) of the bipolar plate (2') to functionalize the surface (O) of the bipolar plate (2'), and - By means of a second material removal method, some portions of the functional layer (10) are selectively removed (400) to expose some areas of the conductive layer material (6).

2. The method according to claim 1, characterized in that, The first material removal method for selectively removing (200) portions of the non-conductive layer material (4) is constructed in the form of an etching method, preferably in the form of a plasma etching method.

3. The method according to claim 1 or 2, characterized in that, The coating method for applying a (300) functional layer (10) on the surface (O) of the bipolar plate (2') is constructed in the form of a vacuum coating method, preferably a PVD method or a CVD method, especially in the form of a plasma-based PVD method or a CVD method.

4. The method according to any one of the preceding claims, characterized in that, Before selectively removing (400) some portions of the functional layer (10), the applied functional layer (10) is dried, wherein the drying of the applied functional layer (10) is preferably achieved by introducing an airflow and / or by irradiation with a radiation source.

5. The method according to any one of the preceding claims, characterized in that, The second material removal method for selectively removing (400) portions of the functional layer (10) is constructed in the form of a mechanical removal method, preferably using a scraper and / or brush and / or compressed air.

6. A bipolar plate (2) for use in a fuel cell, preferably manufactured by processing a bipolar plate (2') made of a composite material (8), particularly according to any one of claims 1 to 5, the composite material comprising a conductive layer material (6) and a non-conductive layer material (4), the bipolar plate comprising: - The first layer (12) has a non-conductive layer material (4). - A second layer (14) disposed on the first layer (12) has a conductive layer material (6) and a functional layer material (10'). -The functional layer material (10') is arranged between the conductive layer materials (6).

7. The bipolar plate (2) according to claim 6, characterized in that, The non-conductive layer material (4) is constructed in the form of plastic, and can be selectively constructed in the form of thermoplastic or thermosetting plastic, especially in the form of polyethylene or polypropylene as thermoplastic plastic or in the form of phenolic resin or epoxy resin as thermosetting plastic.

8. The bipolar plate (2) according to claim 6 or 7, characterized in that, The conductive layer material (6) is constructed in the form of a carbon-containing material, preferably in the form of graphite.

9. The bipolar plate (2) according to any one of claims 6 to 8, characterized in that, The functional layer material (10') includes silicon-containing compounds, preferably siloxanes and / or silanes and / or aminosilanes and / or alkylthiols.

10. The bipolar plate (2) according to any one of claims 6 to 9, characterized in that, The second layer (14) has a layer thickness of <100μm, preferably <10μm, and especially <1μm.

11. A fuel cell having a plurality of bipolar plates (2) according to any one of claims 6 to 10.

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