Method for processing a bipolar plate

Abstract

Method for processing a bipolar plate (2) for use in a fuel cell, comprising the steps of providing (100) a substrate (4) with a top (6) and a bottom (8) to form an anode and a cathode, coating (200) the top (6) and / or the bottom (8) of the substrate (4) in a central area (10a) with a first functional layer (12) and in end areas (10b) with a second functional layer (14), and irradiating (300) the top (6) and / or the bottom (8) of the substrate (4) to dry and functionalize the first and second functional layers (12, 14) by means of radiation (20) in the NIR range.

Description

State of the art

[0001] The present invention is based on a method for processing a bipolar plate and a bipolar plate, preferably manufactured using such a method. Furthermore, the invention relates to a fuel cell comprising a plurality of such bipolar plates. State of the art

[0002] Fuel cells are electrochemical energy converters in which reaction gases, such as hydrogen and oxygen, are converted into water, electrical energy, and heat. The reaction gases are separated by a polymer membrane, which provides the necessary insulation. A fuel cell has a typical symmetrical structure in which a catalyst layer and a gas distribution layer are arranged on either side of the polymer membrane, each of which is in turn connected to a bipolar plate. The bipolar plates arranged within the fuel cell fulfill several functions. They serve to electrically interconnect the cells, to supply and distribute the reaction gases, and to supply and distribute coolant. In order to increase the efficiency of fuel cells, it is known to provide the bipolar plates of a fuel cell with functional coatings.

[0003] After application, the functional coatings must be dried before further processing. According to the state of the art, the functional layers are dried in convection ovens, where they are dried in a continuous oven process. During the continuous oven process, a selected temperature profile is maintained to achieve specified temperature levels.

[0004] Unfortunately, such a continuous furnace process is quite slow due to the large mass and its inertia, especially with large temperature ramps. However, the temperature ramps are necessary to allow gases and solvents to completely escape from the functional layers. Premature drying or sealing of the surface would otherwise lead to cracks and damage in the functional coatings, and complete crosslinking or functional acquisition would not occur. Overall, drying the functional layers of bipolar plates in a continuous furnace process typically takes several hours and is not only time-consuming but also energy-intensive. Disclosure of the invention

[0005] According to a first aspect, the invention relates to a method having the features of the independent method claim and, according to a second aspect, to a bipolar plate according to the independent device claim. According to a third aspect, the invention further relates to a fuel cell having a plurality of bipolar plates according to the independent device claim. Further features and details of the invention emerge from the respective subclaims, the description and the drawings. Features, advantages and details described in connection with the method according to the invention naturally also apply in connection with the bipolar plate according to the invention or the fuel cell according to the invention and vice versa, so that with regard to the disclosure of the individual aspects of the invention, reference is or can always be made reciprocal.

[0006] The method according to the invention for processing a bipolar plate preferably serves to accelerate the manufacturing process of a bipolar plate, in particular to accelerate the drying and functionalization process of a functional coating applied to the surface of a bipolar plate. This enables a significant reduction in cycle times and the elimination of additional process steps. Furthermore, such a processing method not only saves a great deal of time but also a large portion of the required energy, as conventional drying with heat can be dispensed with. This ultimately also means cost savings and positive ecological effects. Finally, by replacing the drying and functionalization sources to be used, a significantly smaller space requirement and lower maintenance costs can be achieved.

[0007] The method according to the invention for processing a bipolar plate for use in a fuel cell comprises the steps of providing a substrate with a top side and a bottom side for forming an anode and a cathode, Coating the top and / or bottom of the substrate in a central region with a first functional layer and in end regions with a second functional layer, as well as irradiating the top and / or bottom of the substrate with radiation in the NIR range to dry and functionalize the first and second functional layers. An end region can be understood, in particular, as a peripheral outer region arranged on a substrate surface.

[0008] The bipolar plate processed using the method according to the invention can preferably be used in a fuel cell or in a fuel cell system for a motor vehicle. Use in other fuel cell-powered means of transport or even stationary systems is also conceivable. It is understood that the method according to the invention is suitable and can be used not only for processing a bipolar plate, but also for processing a monopolar plate or the like, by coating and drying only one of the two sides. In the context of the invention, an anode can be understood in particular as the side of the bipolar plate on which the oxidation reaction takes place. In a fuel cell, the anode is the location where the fuel (e.g. hydrogen) is oxidized, releasing electrons and protons.In the context of the invention, a cathode can also be understood in particular as the side of the bipolar plate on which the reduction reaction takes place. In a fuel cell, the cathode is the location where oxygen (from the air or another source) is reduced by absorbing electrons and protons to form water. The end regions can preferably be arranged at the edge of the bipolar plate and around the port and fluid feedthrough regions arranged on the bipolar plate. Drying can preferably be understood to mean the removal of water and solvents from the functional layers. Functionalization can also preferably be understood to mean a modification of the functional layers brought about by the action of NIR radiation in order to achieve certain desired properties or functions.For the purposes of the invention, radiation in the NIR range can be understood as meaning, in particular, radiation in a frequency range from 750 nanometers (nm) to approximately 2500 nm, preferably up to 1000 nm.

[0009] Within the scope of the invention, it has been recognized that the use of NIR radiation can achieve rapid, effective, and cost-effective drying of functional coatings on bipolar plates. In particular, it has been recognized that, unlike thermal radiation and longer-wavelength IR radiation, NIR radiation can penetrate deeper into the surface of the functional layers, so that the use of NIR radiation not only achieves effective and rapid removal of water and solvents from the functional layers, but also functionalization of the functional layers.

[0010] Within the scope of rapid and efficient drying and functionalization of a first and second functional layer, it can advantageously be provided according to the invention that irradiation of the top and bottom sides of the substrate takes place for drying and functionalizing the first and second functional layers, wherein the irradiation takes place on the top and bottom sides of the substrate simultaneously. With regard to a cost-effective alternative, e.g. with only one radiation source, it can also be provided that the irradiation of the top and bottom sides of the substrate takes place one after the other. It is understood that within the scope of mass processing, a plurality of bipolar plates can also be arranged next to one another and can then be irradiated simultaneously on at least one side.

[0011] With a view to a structurally simple and cost-effective implementation of effective and reliable drying and functionalization of a first and second functional layer, it can advantageously be provided that the irradiation of the top side and / or the bottom side for drying and functionalizing the first and second functional layer is carried out using a quartz radiator, wherein the irradiation is preferably carried out using a first quartz radiator for irradiating the top side and a second quartz radiator for irradiating the bottom side of the substrate. Quartz radiators are particularly suitable for generating radiation in the infrared range that can be easily and precisely adjusted in terms of power and intensity. It is understood that other radiation sources can alternatively be used to generate NIR radiation.

[0012] With a view to particularly fast, effective and at the same time gentle processing of a bipolar plate, it can further be provided that the radiation in the NIR range penetrates into the top and / or bottom of the substrate to a layer depth of at least 15 µm, preferably to a layer depth of 75 µm, when irradiating the top and / or bottom of the substrate.

[0013] With regard to a particularly targeted adjustable radiation in the infrared range with regard to power and intensity, it can advantageously also be provided that the intensity and / or energy of the radiation in the NIR range is adjusted in a targeted manner during the irradiation of the top side and / or the bottom side of the substrate, wherein a modulation method, in particular a pulse width modulation, is preferably used for the targeted adjustment of the intensity and / or energy of the radiation in the NIR range.

[0014] In the context of effective drying and functionalization, it is advantageously conceivable that the first and second functional layers are baked and / or cured and / or foamed and / or crosslinked during drying and functionalization.

[0015] For rapid processing, particularly rapid drying and functionalization, it is advantageously conceivable for the top and / or bottom of the substrate to be irradiated using radiation in the NIR range for a period of less than 30 seconds, preferably for a period of less than 15 seconds, in particular for a period of less than 5 seconds. The use of radiation in the NIR range makes it possible to achieve rapid processing without negatively affecting the layer quality of the functional layers.

[0016] The invention also further relates to a bipolar plate for use in a fuel cell, in particular processed according to a method described above, comprising a substrate with a top side and a bottom side for forming an anode and a cathode, a central region arranged on the top side and bottom side of the substrate with a first functional layer, and an end region arranged on the top side and bottom side of the substrate with a second functional layer, wherein the first and second functional layers are dried and functionalized by irradiation using radiation in the NIR range. The bipolar plate according to the invention thus exhibits the same advantages as have already been described in detail with regard to the method according to the invention. The substrate in question can preferably be formed from a metal material.The central region may also preferably comprise a plurality of distribution channels arranged next to one another, which are arranged on one side on supply channels of a supply region and on the other side on discharge channels of a discharge region.

[0017] The invention furthermore relates to a monopolar plate, in particular processed according to a method described above, comprising a substrate with a top side and a bottom side for forming an anode and a cathode, a central region arranged on the top side or bottom side of the substrate and having a first functional layer, and an end region arranged on the top side or bottom side of the substrate and having a second functional layer, wherein the first and second functional layers are dried and functionalized by irradiation using radiation in the NIR range. The monopolar plate according to the invention thus exhibits the same advantages as have already been described in detail with regard to the method according to the invention or the bipolar plate according to the invention.

[0018] With a view to increasing the efficiency of bipolar plates and optimizing performance, it can advantageously be provided that the first and / or second functional layer has a layer thickness of at least 7 µm, preferably at least 15 µm. Such a layer thickness enables, in particular, low heat losses and efficient conversion of chemical energy into electrical energy. A layer thickness of at least 7 µm, preferably at least 15 µm, can correspond in particular to a wet layer thickness of 15 to 75 µm.

[0019] Likewise, with a view to increasing the efficiency of bipolar plates and optimizing performance, it is conceivable for the first functional layer to comprise a carrier component and a solid component, wherein the carrier component preferably comprises a resin and the solid component comprises graphite, and / or for the second functional layer to be formed from a plastic, preferably from a sealant, in particular a fluororubber sealant. Such a design of the corresponding layers enables, in particular, an optimized adaptation of the layers to the respective functions.

[0020] The invention furthermore relates to a fuel cell comprising a plurality of bipolar plates as described above. Thus, the fuel cell according to the invention exhibits the same advantages as those already described in detail with regard to the method according to the invention and the bipolar plate according to the invention.

[0021] Further advantages, features, and details of the invention will become apparent from the following description, which describes embodiments of the invention in detail with reference to the drawings. The features mentioned in the claims and in the description may be essential to the invention individually or in any combination. They show: Fig. 1 a schematic representation of the individual steps of a method according to the invention for processing a bipolar plate for use in a fuel cell, Fig. 2 a schematic representation of an irradiation of the top and bottom of a substrate of a bipolar plate according to the invention according to a first embodiment, Fig. 3 a schematic representation of the processes occurring during irradiation of the upper side of a substrate of a bipolar plate according to the invention, and Fig. 4 a schematic representation of a bipolar plate according to the invention for use in a fuel cell.

[0022] Fig. 1 shows a schematic representation of the individual steps of a method according to the invention for processing a bipolar plate 2 for use in a fuel cell.

[0023] As per Fig. 1, the method according to the invention comprises the steps of providing 100 a substrate 4 with a top side 6 and a bottom side 8 for forming an anode and a cathode, coating 200 the top side 6 and the bottom side 8 of the substrate 4 each in a central region 10a with a first functional layer 12 and in end regions 10b with a second functional layer 14 and irradiating 300 the top side 6 and the bottom side 8 of the substrate 4 for drying and functionalizing the first and second functional layers 12, 14 by means of radiation 20 in the NIR range.

[0024] Fig. 2 shows a schematic representation of an irradiation of the top side 6 and bottom side 8 of a substrate 4, which is here hidden by the apparatus, of a bipolar plate 2 according to the invention according to a first embodiment.

[0025] As per Fig. 2, the irradiation 300 of the top side 6 and the bottom side 8 of the substrate 4 for drying and functionalizing the first and second functional layers 12, 14 takes place on the top side 6 and the bottom side 8 of the substrate 4 simultaneously, by means of a first quartz radiator 16a for irradiating the top side 6 and a second quartz radiator 16b for irradiating the bottom side 8 of the substrate 4 of the bipolar plate 2. Spacers 18 are arranged between the quartz radiators 16a, 16b and the bipolar plate 2.

[0026] The intensity and / or energy of the radiation 20 in the NIR range can be adjusted in a targeted manner during the irradiation 300 of the top side 6 and the bottom side 8 of the substrate 4, for example via a modulation method, in particular via pulse width modulation.

[0027] The irradiation 300 of the top side 6 and the bottom side 8 of the substrate 4 can take place for a period of less than 30 seconds, preferably for a period of less than 15 seconds, in particular for a period of less than 5 seconds.

[0028] Fig. 3 shows a schematic representation of the processes occurring during irradiation of the upper side 6 of a substrate 4 of a bipolar plate 2 according to the invention.

[0029] As per Fig. As can be seen in Figure 3, the radiation 20 in the NIR range penetrates into the first functional layer 12 during irradiation 300 of the top side 6 of the substrate 4, for example, to a layer depth of at least 15 µm, in particular to a layer depth of 75 µm. This allows, on the one hand, water or solvent molecules 22 to be effectively transported out of the first functional layer 12, and, on the other hand, other layer components 24, such as pigments or the like, within the first functional layer 12 to be functionalized, for example, foamed and / or crosslinked.

[0030] Fig. 4 shows a schematic representation of a bipolar plate 2 according to the invention for use in a fuel cell.

[0031] As per Fig.4, the bipolar plate 2 comprises a substrate 4 with a top side 6 (top image) and a bottom side 8 (bottom image) for forming an anode and a cathode, a central region 10a arranged on the top side 6 and the bottom side 8 of the substrate 4 with a first functional layer 12 (see enlarged section top right) and an end region 10b arranged on the top side 6 and the bottom side 8 of the substrate 4 with a second functional layer 14 (see enlarged section bottom right), wherein the first and second functional layers 12, 14 are dried and functionalized by irradiation using radiation 20 in the NIR range.

[0032] The first and / or second functional layer 12, 14 can, for example, have a layer thickness of at least 7 µm, preferably of at least 15 µm.

[0033] In addition, the first functional layer 12 can have a carrier portion and a solid portion, wherein preferably the carrier portion comprises a resin and the solid portion comprises graphite and / or the second functional layer 14 is formed from a plastic, preferably from a sealant, in particular a fluororubber sealant.

Claims

[1] Method for processing a bipolar plate (2) for use in a fuel cell, comprising the steps: - Providing (100) a substrate (4) with a top side (6) and a bottom side (8) for forming an anode and a cathode, - coating (200) the top side (6) and / or the bottom side (8) of the substrate (4) in a central region (10a) with a first functional layer (12) and in end regions (10b) with a second functional layer (14), - Irradiating (300) the top side (6) and / or the bottom side (8) of the substrate (4) for drying and functionalizing the first and second functional layers (12, 14) by means of radiation (20) in the NIR range. [2] Method according to claim 1, characterized bythat irradiation (300) of the top side (6) and the bottom side (8) of the substrate (4) takes place for drying and functionalizing the first and second functional layers (12, 14), wherein the irradiation (300) on the top side (6) and the bottom side (8) of the substrate (4) takes place simultaneously. [3] Method according to claim 1 or 2, characterized by that the irradiation (300) of the upper side (6) and / or the lower side (8) for drying and functionalizing the first and second functional layer (12, 14) is carried out by means of a quartz radiator (16a, 16b), wherein the irradiation (300) is preferably carried out by means of a first quartz radiator (16a) for irradiating the upper side (6) and a second quartz radiator (16b) for irradiating the lower side (8) of the substrate (4). [4] Method according to one of the preceding claims, characterized bythat the radiation (20) in the NIR range penetrates into the top side (6) and / or the bottom side (8) of the substrate (4) to a layer depth of at least 15 µm, preferably to a layer depth of 75 µm, when irradiating (300) the top side (6) and / or the bottom side (8) of the substrate (4). [5] Method according to one of the preceding claims, characterized by that the intensity and / or energy of the radiation (20) in the NIR range is adjusted in a targeted manner during the irradiation (300) of the top side (6) and / or the bottom side (8) of the substrate (4), wherein a modulation method, in particular pulse width modulation, is preferably used for the targeted adjustment of the intensity and / or energy of the radiation (20) in the NIR range. [6] Method according to one of the preceding claims, characterized bythat the first and second functional layer (12, 14) are baked and / or cured and / or foamed and / or crosslinked during drying and functionalization. [7] Method according to one of the preceding claims, characterized by that the irradiation (300) of the top side (6) and / or the bottom side (8) of the substrate (4) by means of radiation (20) in the NIR range takes place for a period of time of less than 30 seconds, preferably for a period of time of less than 15 seconds, in particular for a period of time of less than 5 seconds. [8] Bipolar plate (2) for use in a fuel cell, in particular processed according to a method according to one of the preceding claims, comprising: - a substrate (4) with a top side (6) and a bottom side (8) for forming an anode and a cathode, - a central region (10a) arranged on the top side (6) and the bottom side (8) of the substrate (4) with a first functional layer (12) and an end region (10b) arranged on the top side (6) and the bottom side (8) of the substrate (4) with a second functional layer (14), - wherein the first and second functional layers (12, 14) are each dried and functionalized by irradiation using radiation (20) in the NIR range. [9] Bipolar plate (2) according to claim 8, characterized by that the first and / or second functional layer (12, 14) has a layer thickness of at least 7 µm, preferably of at least 15 µm. [10] Bipolar plate (2) according to one of claims 8 or 9, characterized bythat the first functional layer (12) has a carrier portion and a solid portion, wherein preferably the carrier portion comprises a resin and the solid portion comprises graphite and / or the second functional layer is formed from a plastic, preferably from a sealant, in particular a fluororubber sealant. [11] Fuel cell comprising a plurality of bipolar plates (2) according to one of claims 8 to 10.

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