Method for coating a dispenser plate for an electrochemical cell

Abstract

The invention relates to a method for coating a distributor plate (7, 8) for an electrochemical cell (100), the distributor plate (7, 8) having channels (11) and elevations (12), characterized by the following method steps: applying a coating (30) to the elevations (12), heating the distributor plate (7, 8) by means of a preheating device (40), and further heating the distributor plate (7, 8) by means of a heater (50).

Description

Technical Field

[0001] The invention relates to a method for coating a distributor plate. The distributor plate is heated by means of a preheating device. The distributor plate is preferably used in an electrochemical cell such as a fuel cell or an electrolysis cell. Background Art

[0002] Fuel cells are electrochemical energy converters in which, for example, hydrogen and oxygen are converted into water, electrical energy and thermal energy; in an electrolyzer, the electrochemical processes take place in the opposite direction. The cell stack of an electrochemical cell is constructed from a multi-piece cell having membrane electrode units and bipolar plates arranged alternately one on top of the other. The bipolar plates are used to supply the electrodes with reactants and to cool the fuel cell stack. For this purpose, the bipolar plates have a distributor structure that guides the fluid containing the reactants along the electrodes; the bipolar plates are usually composed of one or two distributor plates. The distributor structure is usually designed as a channel, which allows different fluids to be guided.

[0003] DE 10 2005 046 461 A1 discloses a coating which is applied to a distributor plate. These coatings can be applied, for example, by means of screen printing. It is known that the coating must dry or harden. Summary of the invention

[0004] The object of the present invention is to achieve very rapid drying / curing.

[0005] For this purpose, a distributor plate for an electrochemical cell is heated by means of a preheating device. The distributor plate has channels and projections. The method for coating a distributor plate is characterized by the following method steps:

[0006] - applying the coating to the protrusions,

[0007] - heating the distributor plate with the aid of a preheating device,

[0008] - Further heat is supplied to the distributor plate in the heater.

[0009] The coating can be applied, for example, by means of screen printing or with a roller.

[0010] Preferably, the preheating device is an induction heating device. With the aid of induction heating, the heat to be supplied to the distributor plate can be metered very precisely. Heat can also be supplied to the distributor plate more quickly than with conventional radiation heating; this can even be up to 1000 times better. Inaccessible components or areas can be heated, such as metal parts embedded (for example in wood, plastic or vacuum). Devices for induction heating require much less space than radiation heating devices. Since the heat is generated in the material itself, the heat radiation and thus the heat losses are very small. As a result, due to the smaller heat and radiation losses, induction heating has a higher efficiency. Heating with induction is additionally carbon dioxide-free.

[0011] In an alternative advantageous embodiment, however, the preheating device can also be embodied as a microwave heating device or as an electromagnetic radiator.

[0012] Preferably, the heating device is a furnace. The furnace is particularly preferably kept at a constant temperature for which it is optimally designed.

[0013] In a preferred embodiment of the method, the distributor plate is held in a heater. The distributor plate and thus the coating are thus subjected to a substantially constant temperature for a certain period of time, so that the drying / curing of the coating takes place over the desired process time. Holding in an oven is more advantageous both energetically and economically than maintaining the temperature with a preheating device.

[0014] The invention is preferably used for distributor plates of electrochemical cells such as fuel cells and electrolyzers. Fuel cells and electrolyzers are in particular PEM-FCs (polymer electrolyte membrane fuel cells) or PEM-ECs (polymer electrolyte membrane electrolyzers).

[0015] In an extended embodiment, the projection can be configured as a sealing structure. The distributor plate for an electrochemical cell usually separates a variety of media from each other, so the flow structures must be sealed to each other. This can be achieved, for example, by a coated sealing structure. This sealing structure can be simply configured as a projection or a sealing bead (Dichtsicke). Especially in the case of a thin metal distributor plate, this sealing structure can be manufactured very simply by means of a molding method. Advantageously, the coating is implemented as an elastomer or an adhesive. The elastomer has very good sealing properties. In other advantageous configurations, the coating is implemented as a conductive paint, especially in order to reduce the resistance between the distributor plate and another component that contacts the distributor plate, such as a diffusion layer.

[0016] In an advantageous embodiment, all elevations of the active region of the distributor plate are coated. The coating is preferably implemented as a conductive lacquer, particularly preferably as a carbon coating. The entire active region is provided with a very low contact resistance at the contact surface of the distributor plate with the underlying layer, usually a diffusion layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Embodiments of the invention are shown in the drawings and explained in more detail in the following description. The drawings show:

[0018] Figure 1 : A schematic cross section of a known electrochemical cell, wherein only essential regions are shown,

[0019] Figure 2 : Section through a known distributor plate with a coating, wherein only essential areas are shown,

[0020] Figure 3: schematically illustrates a method for manufacturing a distributor plate according to the present invention,

[0021] Figure 4 : Schematically shows two heating curves of the distributor plate. DETAILED DESCRIPTION

[0022] Figure 1 An electrochemical cell 100 known from the prior art in the form of a fuel cell is schematically shown, wherein only essential regions are shown. The fuel cell 100 has a membrane 2, in particular a polymer electrolyte membrane. A cathode chamber 100a is formed on one side of the membrane 2, and an anode chamber 100b is formed on the other side.

[0023] In the cathode chamber 100a, the electrode layer 3, the diffusion layer 5 and the distributor plate 7 are arranged outwardly from the diaphragm 2, that is, in the normal direction or the stacking direction z. Similarly, in the anode chamber 100b, the electrode layer 4, the diffusion layer 6 and the distributor plate 8 are arranged outwardly from the diaphragm 2. The diaphragm 2 and the two electrode layers 3, 4 form a membrane electrode assembly 1. In addition, the two diffusion layers 5, 6 are also components of the membrane electrode assembly 1.

[0024] The distributor plates 7, 8 have channels 11 for supplying gas, for example air in the cathode chamber 100a and hydrogen in the anode chamber 100b, to the diffusion layers 5, 6. The diffusion layers 5, 6 are usually composed of carbon fiber fleece on the channel side, i.e. towards the distributor plates 7, 8, and of a microporous particle layer on the electrode side, i.e. towards the electrode layers 3, 4.

[0025] The distributor plates 7, 8 have channels 11 and therefore implicitly also projections 12 adjoining the channels 11. The underside of these projections 12 thus forms a contact surface 13 of the respective distributor plate 7, 8 with the diffuser layer 5, 6 situated underneath.

[0026] Typically, the cathode-side distributor plate 7 and the anode-side distributor plate 8 are different from each other. Advantageously, the cathode-side distributor plate 7 of the electrochemical cell 100 and the anode-side distributor plate 8 of the electrochemical cell adjacent thereto are fixedly connected, for example, by a welded connection and thus combined into a bipolar plate.

[0027] DE 10 2004 009 869 A1 also discloses bipolar plates or distributor plates 7, 8 having channels 11 and projections 12. For this purpose, Figure 2 A detail of a known distributor plate 7, 8 is shown. A coating 30 with an electrically conductive material, here also an electrically conductive lacquer, is applied to the protrusion 12; the electrically conductive lacquer is preferably a carbon coating. Also preferably, the coating 30 can also be corrosion-resistant. The coating 30 can also be a sealing material.

[0028] According to the invention, during the production method of the coating 30, the coating is dried and cured in an oven by means of preheating, for example induction heating, and a subsequent further process. This results in the following advantages:

[0029] The process time for producing the distributor plates 7 , 8 or the bipolar plates is shortened and thus also higher unit quantities or lower investments are possible.

[0030] - Heating the coating 30 from one side of the distributor plate 7 , 8 or the bipolar plate so that no skinning forms.

[0031] Figure 3 The method for producing a distributor plate 7, 8 with a coating 30 according to the invention is schematically shown. The distributor plates 7, 8 or bipolar plates are arranged on a production line moving in a running direction 60. First, the distributor plates 7, 8 with the coating 30 applied thereto are heated or preheated by means of a preheating device 40. Preferably, the distributor plates 7, 8 are then kept warm in a heater 50, in particular in a furnace. This allows the coating 30 to be hardened very quickly. In an advantageous embodiment, the preheating device 40 is implemented as an induction heating device, a microwave heating device or an electromagnetic radiator. This allows the coating 30 to reach the desired temperature very quickly.

[0032] Figure 4 In the temperature T versus time t graph, two heating curves are shown; it can be seen that when in the process chain, the preheating device 40 ( Figure 4 The diagram in FIG. 7 is based on how the heating behavior of the distributor plates 7, 8 or the coating 30 is accelerated when an induction heating device as a preheating device 40 is arranged before the heater 50: Curve 71 shows the temperature behavior of the distributor plates 7, 8 when only a furnace is used as the heater 50 for heating; Curve 72 shows the temperature behavior 72 of the distributor plates 7, 8 when preheating is first performed with the aid of the preheating device 40 and then the temperature in the furnace 50 is maintained. Curves 71a, 72a show the corresponding instantaneous heating phases, and curves 71b, 72b show the corresponding constant holding phases.

[0033] It can be seen that the heating phase 72a with the preheating device 40 is steeper and thus extends faster than the heating phase 71a without preheating. Therefore, the heating time can be reduced by actively bringing the distributor plates 7, 8 to the desired temperature by means of the preheating device 40. The hot distributor plates 7, 8 are then introduced into the furnace 50.

[0034] The distributor plates 7, 8 are preferably metal distributor plates: the preheating device 40, preferably embodied as an induction heating device, heats the metal of the distributor plates 7, 8, whereby the coating 30 hardens from one side of the distributor plates 7, 8 and not from the air side. This reduces the formation of crusts and optimizes the process.

[0035] Instead of an inductive heating device, it is also possible to use electromagnetic radiators, for example infrared radiators.

Claims

1. A method for coating a distributor plate (7, 8) for an electrochemical cell (100), wherein: The distributor plate (7, 8) has a channel (11) and a projection (12), and the method is characterized by the following method steps: - applying a coating (30) to the protrusions (12), - heating the distributor plates (7, 8) by means of a preheating device (40), - Further heat is supplied to the distributor plates (7, 8) by means of a heater (50).

2. The method according to claim 1, characterized in that The preheating device (40) is an induction heating device.

3. The method according to claim 1, characterized in that The preheating device (40) is a microwave heating device.

4. The method according to claim 1, characterized in that The preheating device (40) is an electromagnetic radiator.

5. The method according to any one of claims 1 to 4, characterized in that The heater (50) is a furnace.

6. The method according to any one of claims 1 to 5, characterized in that All projections (12) of the active area of ​​the distributor plates (7, 8) are coated with the coating (30).

7. The method according to any one of claims 1 to 6, characterized in that The coating (30) is a conductive lacquer, in particular a carbon coating.

8. The method according to any one of claims 1 to 7, characterized in that The distributor plates (7, 8) are kept at temperature in the heater (50).

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