DE10124272A1 - Continuous production of polymer electrolyte membrane-electrode array for fuel cell involves coating or impregnating and drying substrate, producing and drying polymer electrolyte membrane in parallel stage and lamination - Google Patents

Abstract

Continuous production of fuel cell polymer electrolyte membrane (PEM)-electrode array involves (a) coating/impregnating and drying a substrate containing carbon and (b) producing a PEM by coating a substrate film with a solution, paste or suspension containing PEM and drying (c) continuously combining the layers from (a) and (b) and removing the substrate film if used in (b). Continuous production of fuel cell polymer electrolyte membrane (PEM)-electrode array involves: (1) coating/impregnating and drying a substrate containing carbon; and (2) producing a PEM by coating a substrate film with a solution, paste or suspension containing PEM and drying or using a ready-made PEM simultaneously in parallel; then (3) continuously combining the layers from (a) and (b) and removing the substrate film if used in (b).

Description

The present invention relates to a method for continuous Nuclear production of a polymer electrolyte membrane electro denanordnung for a fuel cell according to the preamble of Claim 1.

From the older, not previously published document DE 199 62 941 is a method of making a polymer electrolyte membrane electrode assembly for a fuel cell known, in which a self-supporting ion-conducting membrane on a substrate applied to a branch and thus an electrode-membrane composite body is formed, with an ion-conducting as a self-supporting membrane Polymer is used, in which a metal alkoxide Starting material hydrolyzed and / or condensed metal hal gel and / or chemically bonded to the polymer that is.

The object of the invention is to provide a continuous Process for producing a polymer electrolyte membrane Electrode arrangement for a fuel cell, in which the ge closed process chain the process security and thus also the quality of the membrane electrode assemblies (MEA) clearly improved.

This problem is solved by a method with the features of claim 1.

Advantageous embodiments of the method according to the invention are the subject of the subclaims and the description.  

The invention will now become apparent from the accompanying drawings ter described. This shows in a schematic way

Fig. 1 shows an example of a continuous manufacturing process of a polymer electrolyte membrane electrode assembly

Fig. 2 shows an example of a deposition device for electro-chemical deposition of a catalyst

The method according to the invention for producing a polymer electrolyte membrane electrode arrangement for a fuel cell comprises the following method steps:

• a) coating and / or impregnating a carbon-containing Substrate with subsequent drying,
• b) Production of a polymer electrolyte membrane by coating treatment of a carrier film with a PEM-containing solution or Paste or suspension with subsequent drying or Ver application of a finished polymer electrolyte membrane,
• c) merging those obtained from steps a) and b) Layers,
• d) and then when using a carrier film in step b) pulling off this film,

with steps a) and b) parallel and simultaneous leads and the resulting layers continuously are processed further in the third step c).

A flexible, porous, carbon-containing substrate 1 is preferably used as the substrate material for the production of a polymer electrolyte membrane electrode arrangement. This can be a carbon-containing fabric, paper, felt or non-woven. The substrate is coated or impregnated with at least one hydrophobic polymer in the range from 0 to 50 percent by weight in a manner known per se. Furthermore, the substrate material can be provided with at least one buffer layer 2 for controlling the gas and water management. If at least one such buffer layer is present, the substrate is preferably not hydrophobic. The at least one buffer layer contains carbon and / or carbon-containing material and at least one hydrophobic polymer. Teflon is preferably used as the hydrophobic polymer. The teflon content is in the range between 0 and 60% by weight, preferably between 5 and 40% by weight, particularly preferably between 10 and 30% by weight. In a preferred embodiment, at least one further buffer layer is contained on the at least one buffer layer. The at least one further buffer layer contains at least one hydrophobic polymer and / or carbon and / or carbon-containing material.

The teflon content of the at least one further buffer layer is in the range between 0 and 40% by weight, preferably between 0.1 and 10% by weight, particularly preferably the last buffer layer adjacent to the catalyst layer contains no hydrophobic polymer. These buffer layers can be applied in a continuous manner to the substrate in process step a) via a metering unit by means of screen printing, by pouring, brushing on, spraying on, spraying on, knife coating or the like. One or more drying steps 3 and / or temperature treatment steps follow the coating process. The drying process is at temperatures around 80 to 250 ° C, preferably at temperatures around 100 to 200 ° C, the temperature treatment step at temperatures between about 300 ° C and 450 ° C, preferably at temperatures between about 370 ° C and 420 ° C. Subsequently, a measurement of the surface roughness, the thickness and the area weight on the substrate material can be carried out in the online method to ensure a constant quality. In another embodiment, the at least one buffer layer 2 or the at least one further buffer layer is provided with at least one catalyst- or catalyst-containing layer. This layer (s) is or are also applied via a metering unit by means of screen printing, by pouring, brushing, spraying, spraying, knife coating or the like in a continuous manner onto the buffer layer (s) and subsequently at temperatures of about 80 ° C to 450 ° C dried. Furthermore, there is also the possibility of applying a polymer electrolyte membrane-containing solution to the at least one catalyst- or catalyst-containing layer to form a membrane as well via a metering unit by means of screen printing, by casting, spreading, spraying, spraying, knife coating or the like in a continuous manner and subsequently drying at temperatures around 60 ° C to 170 ° C, preferably at temperatures around 60 ° C to 170 ° C.

In method step b), a polymer electrolyte membrane 5 is produced by coating a carrier film 4 . The carrier films used are, for example, polyethylene or polyethylene-containing, teflon or teflon-containing films, polyester or polyester-containing films which have a very homogeneous surface with defined surface roughness for the purpose of adhesion between the carrier film and membrane, a sufficient temperature resistance for temperatures above 120 ° C. have uniform layer thickness. Nevertheless, there cannot be an inseparable bond between the carrier film and the membrane, since the film must be removed again in a further process step. Before the membrane is applied, the carrier film 4 is heated to a temperature in a range from approximately 20 to 90 ° C. The polymer electrolyte membrane 5 is then applied to the carrier film by casting, knife coating, spraying, by means of screen printing or by means of a slot or flat slot nozzle with a melt pump. When using a polymer containing sulfonic acid groups, a phase modification takes place in the range from approximately 110 ° C. to 150 ° C., preferably at approximately 120 ° C., ie the polymer is converted into a conductive form: the sulfonic acid groups fold in the preferred plane and later act as proton channels ,

After the production of the polymer electrolyte membrane, the membrane passes through one to three drying zones 6-8 , depending on the method, the first drying process taking place at a material and process-dependent low temperature and the drying being carried out with the ambient air, preferably in countercurrent, preferably at room temperature, which the second drying process takes place at a material and process-dependent mean temperature and the third drying process takes place at a likewise material and process-dependent higher temperature, the drying at the medium and / or higher temperature preferably being carried out with the inclusion of IR radiators to form the material properties of the membrane becomes.

Of course, a finished membrane 12 produced in one or more upstream process step (s) can also be used, which also includes, for example, a membrane with at least one buffer layer located above it, a membrane with at least one catalyst-containing layer or a membrane with at least one catalyst-containing layer with at least one buffer layer located above.

In the case of a membrane manufactured using the sol-gel method is the raw materials, which are in separate Reservoirs are located together in the dosing unit leads and mixed briefly at room temperature before the mixture, which is transferred to a doctor / roller trough on a Temperature of about 20 to 60 ° C is tempered to a before heated carrier film is applied. As starting materials can polymer-forming hydrocarbon material, e.g. B. the under the Brand name nation available fluorinated hydrocarbon, and at least one metal alkoxide, for example tetraethoxysi lan, be taken. The procedural steps and the training the resulting sol-gel membrane largely corresponds the older, unpublished patent application PCT / EP 00/08465, the steps according to the invention being continuous be performed. The drying times are around 10 to 15 minutes, the drying channel has a temperature between between 110 and 150 ° C.

In the case of a membrane, which is produced by the phase inversion process, the starting materials for the production of a casting compound, which can contain other substances besides the polymer such as. B. reinforcing materials in the form of fibers from polymers, glass or textiles, in separate reservoirs. They are introduced together into the dosing unit and briefly mixed together at room temperature. This mixture, which is heated to a temperature of approx. 70 to 100 ° C in a squeegee / roller trough, is applied to a preheated carrier film, which can optionally contain a highly porous PTFE film in which the PEM Solution can infiltrate, resulting in improved swelling behavior of the membrane. The first drying takes place in a closed volume at approximately 60 to 110 ° C., preferably at approximately 80 ° C., at which a saturation vapor pressure of the solvent used builds up above the material to be dried. In the area facing away from the carrier film, a denser, less porous cover film is formed on the surface, which consists almost 100% of pure polymer. By increasing the solvent concentration above the material to be dried, drying is inhibited in deeper layers, so that no drying cracks form. The material to be dried then passes through a well-ventilated drying zone at a drying temperature of approximately 60 to 110 ° C., preferably approximately 80 ° C., and structures also form in the side facing the carrier film within the lower layers. The drying times in both zones are approximately 1 to 25 minutes, preferably 2 to 10 minutes. In a downstream precipitation bath 9 , the precipitation process is carried out with an organic solvent, preferably with NMP (N-methyl-2-pyrrolidone). The precipitation bath 9 contains deionized water with a temperature in the range from about 0 to 30 ° C., preferably 0 ° C. The structure formation initiated by the previous drying cycle within the membrane is frozen by the time of precipitation, including the polymer distribution state present at that time, by expelling the solvent still present in the membrane layer. The optional aqueous boiling bath 10 downstream of the precipitation bath dissolves the pore formers which may be present in the membrane from the membrane over a period of approximately 1 to 15 minutes at a temperature of approximately 70 to 100.degree. The remaining water and the NMP is removed in a further drying cycle 11 at about 20 to 110 ° C in about 1 to 10 minutes. The asymmetric polymer electrolyte membrane produced in this process largely corresponds to the membrane described in the older, not prepublished patent application PCT / EP 00/08465.

Polymer electrolytes based on Na fion from DuPont, but also membranes based at least of a perfluorosulfonic acid-containing polymer, a fluorinated polymer containing sulfonic acid groups, a polymer based of polysulfones or based on a polysulfone-containing poly mers or a polymer based on polysulfone modifications onen or polysulfone-containing modifications, e.g. B. PES or PSU, a polymer based on polyether ketones, e.g. B. PEEK, PEK or PEEKK, or based on a polyether ketone-containing polymer ren, a polymer based on polybenzimidazoles, based on Ba sis of polyimides, a polymer based on trifluorsty rol how this z. B. described in WO 97/25369 from Ballard is, or on the basis of a composite membrane, such as this play in an older, unpublished font DE 199 43 244 from DaimlerChrysler, in WO 97/25369 or WO / 06337 by Gore / DuPont de Nemours, insert Find.

The individual polymer names should be understood in the broader sense that will; so z. B. under the term polysulfone or Polyether ketone should not only be understood as polymers Include alkyl groups in the chain, but also those around summarize the aryl groups or generally aromatic groups in included in the chain.

A preferred membrane has one or more of the above called polymers and / or copolymers and / or polymer blends on.

In order to ensure a constant high quality the running of the dried membrane in the laminating continuously exceed the thickness and basis weight checks their dimensional accuracy for the subsequent work steps is critical. This measure is  necessary to extreme the reject rate at the end of the process to keep low.

Due to the optimal setting of the process parameters in the con continuous procedures and quality control be already in the production of the two starting materials (fleece and membrane) for producing a membrane electrode arrangement, it is ensured that the later use of the MEA in the quality required by the fuel cell safely and cost-effectively is achieved.

The layers obtained from steps a) and b) are combined in a process step c) preferably by means of a continuously operating double belt press 13 . Double belt presses with isobaric pressure distribution are preferably used so that a defined pressure can be set in the entire contact or laminating or reaction area of the press. To generate such a reaction zone pressure, there is at least one fluid pressure cushion in a pressure chamber of the press arranged behind the press belt. In order to obtain pressure zones with different isobaric pressures, the pressure chamber is divided into individual, mutually independent, pressurized, mutually sealed fluid cushions.

Furthermore, a double belt press is used, in which one Reaction or contact zone in one or more areas is divided, which is heated and / or cooled or and the one or more areas with the same or different temperatures can be applied. The zones can be directly heated electrically or indirectly via a liquid heat transfer medium can be heated or cooled. To produce a membrane electrode assembly using a Double belt press is run through a temperature program at in a first step the reaction zone or contact zone heated up to a material-dependent, predetermined temperature, this temperature a defined time that depends on the material is held, and if necessary in a second step the Temperature is cooled to a further temperature, this  Temperature held for a defined time before in a last step the device is cooled to room temperature. The double belt presses preferably work at one speed speed from 0.5 to 30 m / min.

To prevent tearing of the film web and an even The double belt press can ensure smooth running a so-called web buffer in the form of a pendulum pulley and / or controlled rewinder and / or unwinder pre-and / or downstream.

Generally, however, isochore double belt presses, i. H. roller-supported presses with built-in roller bed, turned be set. Also normal roll-laminating units or units connected several times in succession, such as from known in the calendering area, can be used for lamination Find.

Following step c) and / or d) (pulling off 14 of the carrier film 4 ) in a further step e) a catalyst material is applied by means of electrochemical deposition 15 through a poly merelectrolyte membrane 5 , 12 , ie the catalyst material is in a transition area between the membrane's 5 , 12 and buffer layer 2 (in the case of several buffer layers between the membrane and the buffer layer which is the most distant from the substrate 1 ). This can be done in a continuous manner or in a separate step. For this purpose, a deposition apparatus as shown in FIG. 2 is connected, which consists of a roller trough 23 , which is also designed as a working electrode, that is to say a cathode. The roller 22 rolling therein has a sealing ring 21 on its peripheral edges and is formed between the sealing rings, ie it has a taper. The roller 22 itself is designed as a counter electrode, here anode, and transports the continuous material web 20 , which is composed of substrate 1 , at least one buffer layer 2 and at least one polymer electrolyte-containing layer 5 , 12 . The sealing ring 21 itself presses the material web 20 passing through between the trough and the roller ze against the working electrode and at the same time seals the substrate side 1 against the separating solution 24 . The roller has perforations through which this separation solution flows in as a fresh solution or can be removed as a used solution. The deposition solution consists of one or more complex salts, dissolved in a solvent, of one or more catalysts, which are primarily metals of Group VIb, VIIIb and / or Ib. Hexachloroplatinic acid (H ₂ PtCl ₆ × 6 H ₂ O) with a content of 5 g / l in 0.1 M sulfuric acid is preferably used as the deposition solution. In addition to a substrate, the material web contains at least one buffer layer and at least one layer containing polymer electrolyte membrane, the latter facing the counter electrode. The catalyst contained in the solution is electrochemically deposited through the membrane into a transition region between the membrane and the buffer layer, specifically onto the buffer layer which is the most distant from the substrate. The transition area can be fuzzy and irregular. The deposition is preferably carried out at a given potential or voltage specification. The separation takes place at room temperature or at temperatures up to 80 ° C. The deposition time ranges from 2 to approx. 20 min, depending on the temperature. The separation parameters include an offset range of at least 1.3 to at least 1.5 volts, an amplitude of at least 1.3 volts and a voltage profile (e.g. direct voltage with superimposed square wave, sine or triangular voltage) in a frequency range between 6 Hz to max. 2 kHz. The deposition can also be carried out by means of direct current with a voltage of approximately 1 to 3 volts, preferably approximately 1.3 to 1.5 volts. The deposition can also be carried out by means of direct current with a voltage of approximately 1.5 volts. Depending on the catalyst or catalyst alloy used, the separation parameters must be adjusted variably.

Following step c) and / or d) and / or e) in a further step f) of the continuous process, a membrane electrode arrangement 16 designed according to claims 1 to 9 is provided with a further membrane electrode arrangement 17 which is parallel and simultaneously to the first membrane electrode arrangement or is produced in a separate working step according to claims 1 to 9, assembled on the membrane side. This lamination step is also preferably carried out by means of a double belt press 18 with isobaric pressure distribution. However, isochore double belt presses or normal roll laminating units can also be used.

In another embodiment, a further layer 19 containing polymer electrolyte membranes can be fed in a method step g) in a continuous manner during the execution of method step f) on the membrane side between the two electrode arrangements. The lamination is also preferably carried out here by means of a double belt press.

In a further embodiment, a composite between two membrane electrode assemblies by spraying a poly merelectrolyte-containing solution and / or a solvent membrane side on the membrane electrode assemblies and through Merge the two membrane electrode assemblies under Pressure and temperature are generated.

Claims (18)

1. A method for the continuous production of a polymer electrolyte membrane electrode assembly for a fuel cell comprising the following process steps

• a) coating and / or impregnation of a carbon-containing substrate with subsequent drying,
• b) production of a polymer electrolyte membrane by coating a carrier film with a PEM-containing solution or paste or suspension with subsequent drying or use of a finished polymer electrolyte membrane,
• c) bringing together the layers obtained from steps a) and b),
• d) and if a carrier film is used in step b), then peeling off this film,

wherein steps a) and b) are carried out in parallel and simultaneously and the resulting layers are continuously processed in the third step c). 2. The method according to claim 1, characterized, that the substrate with at least one hydrophobic polymer in Range from 0 to 50 percent by weight coated or impregnated is renated. 3. The method according to claim 1, characterized, that the substrate with at least one buffer layer for control gas and water management.   4. The method according to claim 1, characterized, that following step c and / or d in another Step e an electrochemical catalyst material Deposition through a polymer electrolyte membrane in a transition area between the polymer electrolyte membrane and Buffer layer (s) is applied. 5. The method according to claim 3, characterized, that the at least one buffer layer with at least one Ka Talysator- or catalyst-containing layer is provided. 6. The method according to claim 1, characterized, that the polymer electrolyte membrane by pouring, knife coating, fuel zen, screen printing or using a flat slot or flat slot nozzle is applied to the carrier film using a melt pump. 7. The method according to claim 1, characterized, that as a polymer electrolyte membrane based on polymer electrolytes from the nation of DuPont, but also membranes based on min least a perfluorosulfonic acid-containing polymer, a fluo rated polymer containing sulfonic acid groups, a polymer Based on polysulfones or based on a polysulfone Polymers or a polymer based on polysulfone Modifications or modifications containing polysulfone, one Polymers based on polyether ketones or based on a polymers containing polyetherketone, a polymer based on Polybenzimidazoles, based on polyimides, a polymer based on trifluorostyrene or based on a composite membrane can be used.   8. The method according to claim 1, characterized, that a polymer electrolyte membrane by a sol-gel process or is produced by phase inversion. 9. The method according to claim 8, characterized, that in the manufacture of the polymer electrolyte membrane depending on Processes go through one to three drying zones where in the first drying process for a material and process dependent low temperature takes place and the drying tion with the ambient air, preferably in countercurrent the second drying process for a material and process-dependent mean temperature and the third Drying process in a likewise material and process dependent higher temperature takes place, the drying at the medium and / or higher temperature, preferably un ter inclusion of IR emitters to train the material properties of the membrane is made. 10. The method according to claim 1, characterized, that the merge of the steps a) and b) received layers in process step c) by means of a con continuously working double belt press. 11. The method according to claim 10, characterized, that a double belt press with isobaric pressure distribution turned on is set. 12. The method according to claim 11, characterized, that a double belt press is used, which in several Pressure zones is divided, the pressure zones being the same or can have different isobaric pressure.   13. The method according to claim 12, characterized, that a double belt press is used, in which a Reakti ons or contact zone divided into one or more areas which is or are heated and / or cooled and the one or more areas having the same or different temperature can be applied. 14. The method according to claim 13, characterized, that the double belt press at a speed of 0.5 to 30 m / min works. 15. The method according to claim 10 to 14, characterized, that a tempe for producing a membrane electrode assembly program is carried out in a first step the reaction zone or contact zone to a material-dependent, predetermined temperature heated, this temperature defi nated time, which is dependent on the material, and at In a second step, the temperature needs another Temperature is cooled, this temperature is a defined Time held before the device in a final step is cooled to room temperature. 16. The method according to claim 1 to 15, characterized, that following step c) and / or d) and / or e) in one a further step f) of the continuous process claims 1 to 9 membrane electrode assembly with a further membrane electrode arrangement which is parallel and simultaneously with the first membrane electrode arrangement or in egg Nem separate step according to claims 1 to 9 Herge is put together on the membrane side.   17. The method according to claim 16, characterized, that another polymer electrolyte membrane-containing layer in a process step g) in a continuous manner during the execution of process step f) between the membrane side both membrane electrode assemblies is fed. 18. The method according to claim 16 and 17, characterized, that the composite obtained in process step g one at the The cutting and / or punching arranged on the outlet side of the system operation is subjected, the punch press simultaneously is provided with a stacking device and waste strip collector.