DE102006054737A1 - Use of an ionic liquid based on fluorinated or partially fluorinated alkyl phosphorus/phosphine, phosphonic- or alkyl sulfonic-acid, or di- or triacid derivatives as an electrolyte to prepare fuel cell membrane or its electrode assemblies - Google Patents

Abstract

Use of an ionic liquid on the basis of fluorinated or partially fluorinated alkyl phosphorus/phosphine, phosphonic- or alkyl sulfonic- acid, or on the basis of derivatives of di- or triacid as an electrolyte for preparing fuel cell membrane or fuel cell membrane electrode assemblies, is claimed. An independent claim is included for the ionic liquid comprising a first composition comprising 1,1-dimethylpyrrolidinium bis(perfluoroalkyl)phosphinate with bis(perfluoroalkyl)phosphinic acid and 1,1-dimethylpyrrolidinium perfluoroalkylphosphonate with perfluoroalkylphosphonic acid in a weight ratio of 1:1; a second composition comprising 1,1-dimethylpyrrolidinium-perfluoroalkylfluorophosphate (VI) and triethyleneglycoldimethylether-perfluoroalkylfluorophosphoric acid complex (VII) in a weight ratio of 1:1, where the second composition optionally combines with phosphoric acid; a third composition comprising (VII) and polyethyleneglycol-200-trisperfluoroalkylfluorophosphoric acid complex (VIII), in a weight ratio of 1:1; guanidinium-perfluoroalkylfluorophosphate of formula ([(R2N)3C]+>[(CnF2n+1)6-zPFz]) (IX); protonated polyethyleneimine (a proton per unit) of formula ((-NDiethyletherDiethylethern per Unit) of formula ((-NH-CH(R1a)-CH(R1a)-N(CH(R1a)-CH(R)-CR2>)-CH(R1a)-CH(R1a)-)x.2xH+>[(CnF2n+1)6-zPFz->]) (XI) in combination with (I)-(V), phosphoric acid and its derivative; protonated polyethyleneglycol of formula (-(O-CH(R1a)-CH(R1a)-)5x.xH+>[(CnF2n+1)6-zPFz]->) (XII) in combination with compounds from perfluoroalkylphosphoric acid hydrate of formula (H+>[(CnF2n+1)6-zPFz]yH2O) (I), perfluoroalkylphosphoric acid in diethylether of formula (H+>[(CnF2n+1)6-zPFz].y(C2H5)2O) (II), bis(perfluoroalkyl)phosphinic acid of formula (CnF2n+1)2P(O)(OH) (III), perfluoroalkylphosphonic acid ((CnF2n+1)P(O)(OH)2) (IV) and fluorinated or partially fluorinated alkylsulfonic acid of formula ((CnF2n+1-tHt)SO3H) (V), where the compounds (I)-(V) is present in mixture or composition form, or contains further liquid electrolytes, phosphoric acid and its derivatives; alkylated poly(melamine-co-formaldehyde) of formula (XIII) in combination with (I)-(V), phosphoric acid and its derivative, preferably as di-[perfluoroalkylfluorophosphate]; and poly[N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-alpha ,omega -diamine-CO-2,4-dichloro-6-morpholino-1,3,5-triazine] of formula (XIV) in combination with (I)-(V) phosphoric acid and its derivatives, preferably as pentaperfluoroalkylfluorophosphate. n : 1-8; z : 2-5; R : H or 1-8C-alkyl; R1a : H or 1-4C-alkyl; and m : 0-10. In formula (I):y = +- 3. In formula (II):y = +- 2. In formula (V): t : 0-4, when n is 1 t is 0-2. [Image] [Image].

Description

The Invention relates to the use of ionic liquids comprising fluorinated or partially fluorinated alkyl phosphorus / phosphine or phosphonic acids, fluorinated or partially fluorinated alkylsulfonic acids and / or their derivatives as electrolytes for the production of moisture independent fuel cell membranes and Fuel Cell Membrane Electrode Units (MEA) with Advanced Operating temperature range. Preferably, ionic liquids used which comprise at least one perfluoroalkyl group.

During the Operation of a Polymer Electrolyte Membrane (PEM) Fuel Cell becomes an oxygen-containing gas of the cathode and a hydrogen-containing Gas supplied to the anode. At the anode, the electrochemical oxidation of hydrogen takes place instead, hydrogen formation at the cathode. Through the direct implementation from chemical to electrical energy bypassing the Carnot limitation can be achieved in fuel cells high efficiency.

Developed at the time most PEM fuel cell technology is based on Nafion ^® membranes as the electrolyte. The electrolytic conduction takes place via hydrated protons, whereby the proton conductivity of the membrane is coupled to the presence of water. This limits the operating temperature at normal pressure below 100 ° C. At temperatures higher than 80-95 ° C, performance deteriorates significantly due to increasing water loss. To maintain the conductivity of the membrane above 100 ° C due to the temperature dependence of the vapor pressure of water very large amounts of water to moisten the membrane necessary. In systems with a pressure greater than normal pressure, the temperature can be increased at the expense of the efficiency, size and weight of the overall system. However, for operation well above 100 ° C, the required pressure would increase dramatically.

operating temperatures greater than 100 ° C, however for a variety of reasons desirable: the electrokinetics, as well as the catalytic activity for both Electrodes increase with increasing temperature. Besides that is the tolerance Impurities of the operating gases used, such as Carbon monoxide (CO) higher. For the Use of a fuel cell in a vehicle is due to the lower heat output through the exhaust one as possible size Temperature difference to the ambient temperature for the removal of waste heat advantageous.

There However, with increasing operating temperature the demands on the thermal stability all components of the fuel cell stack and the system components dramatically increases, is for the vehicle use a continuous operating temperature of 120 to 130 ° C as ideal considered. The decisive factor is that one intended for the vehicle drive Electrolyte membrane only a small dependence of the conductivity of the temperature has, so that even at a starting temperature in the room temperature and below sufficient power the MEA is ensured to the system due to the arising thermal waste heat to the continuous operating temperature.

A promising approach, one without or with very little additional humidification operating at operating temperatures of 120 to 180 ° C working fuel cell is, inter alia, in the patents WO 96/13872 A1 . US 5525436 A . US 5716727 A . US 6025085 A . US 5599639 A . WO 99/04445 A1 . EP 983134 B1 . WO 01/18894 A . EP 0 954544 B1 and WO 01/18894 A2 described. The conductivity of here. used fuel cell membrane is based on liquid bound by electrostatic complex binding to the polymer backbone mineral acids (usually phosphoric acid), which takes over the proton conductivity (LF) even with complete dryness of the membrane (above the boiling point of water) without additional humidification of the operating gases. A disadvantage of this system is the fact that the LF, which is lower by a factor of 20, is lower in the room temperature range than the continuous operating temperature (160 ° C.). In addition, the liquid only electrostatically bound to the polymer electrolyte tends to discharge through the at lower temperatures, such as liquid during the start of the cell product water.

Other approaches are based on conventional low-temperature (NT) membranes based on Nafion ^® or sPEEK, in which in the membrane synthesis, for example, by sol-gel processes produced additional inorganic phases (SiO ₂ , B ₂ O ₃ , ZrP, ZrPPh) are introduced. These act on the one hand as a water reservoir, or, especially at higher temperatures, as an additional proton conductor. Corresponding approaches are being pursued worldwide (see EP 92675461 . WO 03/081691 A2 . WO 02/05370 A1 ). In particular, the long-term stability in the range of high operating temperatures and low moisture contents of the operating gases proves to be problematic in this type of membrane. Also, the desired performance at operating temperatures above 100 ° C and low humidities still far below expectations.

Theoretical considerations led to liquid imidazoles as promising proton transfer agents ( US 6264857 A . DE 19632285 A1 , Electrochimica Acta 43 (1998), p. 1281). By covalent attachment of imidazoles to various polymers quite promising model compounds for novel proton conductors have been realized (Pu, Macromolecular Chemistry & Physics 202 (2001) p 1478, Herz, Electrochimica Acta 2002). However, the previously observed proton conduction is still orders of magnitude below that of the conventional Nafion electrolytes, moreover, the compounds have a clear temperature dependence. Furthermore, no carrier polymers stable under the particular conditions of a fuel cell could be identified.

Another approach to the realization of high temperature membranes is based on alkoxysilanes functionalized with organic substituents (sulfonic acid / sulfonamide / imidazole) (for example DE 10163518 A1 . EP 1323767 A2 ). The conductivities observed here are in the order of magnitude of Nafion in the higher temperature ranges at least when moistened, but at lower temperatures the conductivity breaks down significantly.

In recent years, so-called ionic liquids (ionic liquids), ie between room temperature and about 100 ° C already liquid salts are mentioned as promising candidates for the realization of novel anhydrous proton conductors ( WO 01/93362 A1 . US 6667128 B2 ). These compounds are so-called designer solvents, ie their chemically physical properties (solubility / conductivity / boiling / melting temperature, vapor pressure) can be tailored in a wide field for the desired application. The compounds usually consist of organic cations based on nitrogen-containing heterocycles (imidazole, pyridine) in combination with inorganic anions (AlCl ₄ ^- , BF ^- , N (SO ₂ CF ₃ ) ₂ ^- , PF ₃ ^- ). Depending on the constituents used, proton conductivities up to 0.016 S / cm have been observed over a wide temperature range in these systems under anhydrous conditions ( WO 03/083981 A1 ).

The task of a proton-exchanging membrane for fuel cells is in addition to the actual proton conduction and the electrical isolation of the two half-cells in the spatial separation of the reaction gases hydrogen and oxygen. In order to make this possible, ionic liquids must either be embedded in a suitable porous support framework ( WO 03/063266 A2 ) or ideally by polymerization with one another, for example by polycondensation reactions of nitrogen-containing heterocycles can form a self-supporting network (see, inter alia, M. Watanabe, K.-I. Ota, ECS Meeting Honolulu 2005). In the supported variants, there are approaches to incorporate the ionic liquids in about porous matrices, which ensure the mechanical stability, but allow proton conduction over channels filled with ionic liquid. The porous supports are either polymers (PTFE, PET, for example: WO 01/093362 A1 . WO 03/063266 A2 . US 6299653 A . EP 309259 B1 ) or oxidic, preferably nanoparticulate, systems (Al ₂ O ₃ / SiO ₂ , for example: WO 02/047802 A1 ). As an alternative, the impregnation of conventional proton exchange membranes based on sulfonated polymers offers; For example, when Nafion is impregnated with 1-butyl-3-methyl-imidazolium trifluoromethanesulfonate, a conductivity of 0.11 S / cm at 180 ° C and complete dryness is observed (see, inter alia, M. Doyle, Journal of The Electrochemical Society, 147 (1) 34-37 (2000)), other approaches are also based on Nafion or BPSH, which are impregnated with 1-ethyl-3-methylimidazole bis (penta / trifluoroethylsulfonyl) imide (inter alia E. McGrath, ECS Meeting Honolulu 2005).

In summary It should be noted that current Proton exchange membranes for PEM fuel cells a limited one have maximum application temperature and a high moisture requirement. About that In addition, the conductivity shows a distinct one. dependence from the operating temperature.

It was therefore the object of the invention for ionic liquids To look for proton-conducting electrolyte membranes with extended Operating temperature range and reduced humidity requirements lead.

Your Function as a proton conductor results in ionic liquids on the one hand as high-boiling proton solvent (substitution of Water), on the other hand as an intrinsic proton conductor with its own covalently or ionically bound proton-conducting groups, the a sufficient proton conductivity even under liquid-free conditions enable.

According to the invention, novel polymer-bound or free-state stable proton conductors based on ionic liquids are provided as electrolytes for the production of fuel cell membranes or of fuel cell membrane electrode assemblies (MEA). The object of the invention is achieved by the Ver use of ionic liquids based on fluorinated or partially fluorinated alkylphosphorus - / - phosphine or -phosphonic acids, alkylsulfonic acids or derivatives thereof. Particular preference is given to using ionic liquids which comprise at least one perfluoroalkyl group. The invention also provides the use of compositions comprising these compounds and derivatives.

• a) Perfluoralkylphosphorsäure Hydrat (1) H⁺[(C_nF_2n+1)_6-zPF_z]·yH₂O mit n = 1 bis 8, 2 ≤ z ≤ 5, y ≥ 3
• b) Perfluoralkylphosphorsäure in Diethylether (2) H⁺[(C_nF_2n+1)_6-ZPF_z]·y(C₂H₅)₂O mit n = 1 bis 8, 2 ≤ z ≤ 5, y ≥ 2
• c) Bis(perfluoralkyl)phosphinsäure (3) (C_nF_2n+1)₂P(O)(OH) mit n = 1 bis 8
• d) Perfluoralkylphosphonsäure (4) (C_nF_2n+1)P(O)(OH)₂ mit n = 1 bis 8
• e) fluorierte oder teilfluorierte Alkylsulfonsäuren (C_nF_2n+1-tH_t)SO₃H mit n = 1 bis 8, t = 0 bis 4; bei n = 1, t = 0 bis 2
• f) Zusammensetzung (5) 1,1-Dimethylpyrrolidinium Bis(perfluoralkyl)phosphinat: Bis(perfluoralkyl)phosphinsäure; (1:1 w/w)
  
  bzw. 1,1-Dimethylpyrrolidinium mit Perfluoralkylphosphonat: Perfluoralkylphosphonsäure (C_nF_2n+1)P(O)(OH)O (C_nF_2n+1)P(O)(OH)₂ n = 1 bis 8
• g) Zusammensetzung (6) [1,1-Dimethylpyrrolidinium-perfluoralkylfluorphosphat]:[Triethylenglycol-dimethyletherperfluoralkyl fluorphosphorsäure Komplex] (1:1 w/w)
  
  n und z = o.g. Bedeutung
• h) Zusammensetzung (7) [1,1-Dimethylpyrrolidinium-perfluoralkylfluorphosphat]:[Polyethylenglycol-200-trisperfluoralkylfluorphosphorsäure Komplex]; (1:1 w/w)
  
  n und z = o.g. Bedeutung
• i) Guanidinium perfluoralkylfluorphosphat (8) [(R₂N)₃C]⁺[(C_nF_2n+1)_6-zPF_z]^– R = H oder/und C₁-C₈-Alkyl; n und z = o.g. Bedeutung
• j) Protoniertes Polyethylenimin (ein Proton per Unit) in Kombination mit einer Verbindung a) bis e), vorzugsweise als Verbindung (9)
  
  R = H und/oder C₁-C₄-Alkyl; n und z = o.g. Bedeutung
• k) Protoniertes Polyethylenimin (zwei Protonen per Unit) in Kombination mit einer Verbindung a) bis e), vorzugsweise als Verbindung (10)
  
  R = H und/oder C₁-C₄-Alkyl; n und z = o.g. Bedeutung
• l) Protoniertes Polyethylenglycol in Kombination mit einer Verbindung a) bis e), vorzugsweise als Verbindung (11)
  
  R = H und/oder C₁-C₄-Alkyl; n und z = o.g. Bedeutung
• m) Alkyliertes Poly(melamin-co-formaldehyd) in Kombination mit einer Verbindung a) bis e), vorzugsweise als Di-[perfluoralkylfluorphosphat] (12)
  
  R = H und/oder C₁-C₄-Alkyl; n und z = o.g. Bedeutung
• n) Poly(N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-α,ω-diamin-co-2,4-dichlor-6-morphoino-1,3,5-triazin] in Kombination mit einer Verbindung a) bis e), vorzugsweise als Penta-perfluoralkylfluorphosphat)] (13)
  
  R = H und/oder C₁-C₄-Alkyl; n und z = o.g. Bedeutung

Preference is given to the use of the compounds a) to e), which can be used individually, mixed with one another, in compositions or with further liquid electrolytes known per se. Particular preference is also given to the compositions according to the invention having the structures f) to n), if appropriate in combination with at least one of the compounds a) to e).

• a) Perfluoroalkyl phosphoric hydrate (1) H ⁺ [(C _n F _{2n + 1} ) _6-z PF _z ] .yH ₂ O with n = 1 to 8, 2 ≦ z ≦ 5, y ≥ 3
• b) Perfluoroalkyl phosphoric acid in diethyl ether (2) H ⁺ [(C _n F _{2n + 1} ) _6-Z PF _z ] .y (C ₂ H ₅ ) ₂ O with n = 1 to 8, 2 ≦ z ≦ 5, y ≥ 2
• c) bis (perfluoroalkyl) phosphinic acid (3) (C _n F _{2n + 1} ) ₂ P (O) (OH) with n = 1 to 8
• d) perfluoroalkylphosphonic acid (4) (C _n F _{2n + 1} ) P (O) (OH) ₂ with n = 1 to 8
• e) fluorinated or partially fluorinated alkylsulfonic acids (C _n F _{2n + 1-t} H _t ) SO ₃ H with n = 1 to 8, t = 0 to 4; at n = 1, t = 0 to 2
• f) Composition (5) 1,1-dimethylpyrrolidinium bis (perfluoroalkyl) phosphinate: bis (perfluoroalkyl) phosphinic acid; (1: 1 w / w)
  
  or 1,1-dimethylpyrrolidinium with perfluoroalkylphosphonate: perfluoroalkylphosphonic acid (C _n F _{2n + 1} ) P (O) (OH) O (C _n F _{2n + 1} ) P (O) (OH) ₂ n = 1 to 8
• g) Composition (6) [1,1-dimethylpyrrolidinium-perfluoroalkylfluorophosphate]: [triethylene glycol dimethyl ether perfluoroalkyl fluorophosphoric acid complex] (1: 1 w / w)
  
  n and z = og meaning
• h) Composition (7) [1,1-dimethylpyrrolidinium-perfluoroalkylfluorophosphate]: [polyethyleneglycol-200-trisperfluoroalkylfluorophosphoric acid complex]; (1: 1 w / w)
  
  n and z = og meaning
• i) guanidinium perfluoroalkyl fluorophosphate (8) [(R ₂ N) ₃ C] ⁺ [(C _n F _{2n + 1} ) _6-z PF _z ] ^- R = H or / and C ₁ -C ₈ -alkyl; n and z = og meaning
• j) Protonated polyethyleneimine (one proton per unit) in combination with a compound a) to e), preferably as compound (9)
  
  R = H and / or C ₁ -C ₄ -alkyl; n and z = og meaning
• k) Protonated polyethyleneimine (two protons per unit) in combination with a compound a) to e), preferably as compound (10)
  
  R = H and / or C ₁ -C ₄ -alkyl; n and z = og meaning
• l) Protonated polyethylene glycol in combination with a compound a) to e), preferably as compound (11)
  
  R = H and / or C ₁ -C ₄ -alkyl; n and z = og meaning
• m) Alkylated poly (melamine-co-formaldehyde) in combination with a compound a) to e), preferably as di- [perfluoroalkylfluorophosphate] (12)
  
  R = H and / or C ₁ -C ₄ -alkyl; n and z = og meaning
• n) poly (N, N'-bis (2,2,6,6-tetramethyl-4-piperidinyl) -α, ω-diamine-co-2,4-dichloro-6-morphoino-1,3,5- triazine] in combination with a compound a) to e), preferably as penta perfluoroalkyl fluorophosphate)] (13)
  
  R = H and / or C ₁ -C ₄ -alkyl; n and z = og meaning

• 1. Zersetzungstemperatur der Verbindungen deutlich oberhalb der angestrebten Einsatztemperatur (> 150 °C).
• 2. Siedetemperatur deutlich oberhalb der angestrebten Einsatztemperatur (>150°C).
• 3. Leitfähigkeit bei –20 °C (trocken): > 0,01 S/cm.
• 4. Leitfähigkeit bei 20 °C (trocken): > 0,05 S/cm.
• 5. Leitfähigkeit bei 80–130 °C (trocken): > 0,1 S/cm.
• 6. Hohe Oxidationsstabilität (Sauerstoff + Radikale).
• 7. Hohe Reduktionsstabilität, insbesondere gegenüber Wasserstoff.
• 8. Geringe Wasserlöslichkeit über gesamten Einsatztemperaturbereich.

The invention is realized according to the claims. The derivatives used according to the invention are suitable as ionic liquid or its component suitable chemicals. For use as a proton conductor in the PEM fuel cell, the following properties are required:

• 1. Decomposition temperature of the compounds significantly above the desired use temperature (> 150 ° C).
• 2. Boiling temperature well above the desired operating temperature (> 150 ° C).
• 3. Conductivity at -20 ° C (dry):> 0.01 S / cm.
• 4. Conductivity at 20 ° C (dry):> 0.05 S / cm.
• 5. Conductivity at 80-130 ° C (dry):> 0.1 S / cm.
• 6. High oxidation stability (oxygen + radicals).
• 7. High reduction stability, especially with respect to hydrogen.
• 8. Low water solubility over the entire operating temperature range.

Depending on the structure, the derivatives are suitable for the impregnation of porous (membrane matrices) media, as well as for direct membrane production, for example in a drawing process from a suitable solvent. Alternatively, polymers known per se may be impregnated with the novel proton conductors, if appropriate in dilution or solution in a suitable solvent. In a preferred embodiment of the invention, for example, the phosphoric acid in the membrane or electrode in the PBI (polybenzimidazole) / H ₃ PO _{4 system is} replaced by a suitable above-mentioned ionic liquid or fluorinated acid a) to e).

The Derivatives are made with known polymers and / or polymer membrane matrices used, with the membranes or electrodes / MEAs optionally also already with other known liquid electrolytes, preferably with phosphoric acid, equipped could be. Alternatively, the ionic liquid, preferably a) to e), are also introduced only into the electrode, while the membrane with phosphoric acid waterproof remains. The polymer matrices known per se are, for example subsequently with the derivatives of the invention impregnated. In another embodiment The derivatives are used directly in the solution in the preparation of Membranmatrices used or directly in the polymerization.

alternative can the derivatives for the production of an MEA also by soaking the Electrode or preparation of the paste can be used, preferably the derivatives are used directly to soak the electrode on the to a membrane-facing side or in a solution to Painting, spraying or with a vaporizable solvent used to coat the electrode.

Opposite one Fuel cell with phosphoric acid in the electrodes, the cathode losses are lower, which in particular the power is increased at lower temperatures. Part of the Invention is the production of proton-conducting membranes from these Compounds, their use in fuel cells, and their manufacture adapted electrodes using these compounds.

• 1. Verwendung von Verbindungen mit den Strukturen a) bis n) [insbesondere Verbindungen (1) bis (13), bevorzugt (1) bis (8)], als Imprägnierungsmittel in Brennstoffzellenmembranen, die auf der Imprägnierung eines in der Regal basischen Polymers (zum Beispiel PBI) mit Flüssigelektrolyt beruhen (gemäß WO 96/13872 A , US 5525436 A , US 5716727 A , US 6025085 A , US 5599639 A , WO 99/04445 A , EP 983134 B1 , WO 01/18894 A , EP 954544 A1 und WO 01/18894 A2 , US 6124060 A ). Gegebenenfalls erfolgt auch eine Verwendung von entsprechenden Di- oder Triphosphonsäuren und Sulfonsäuren, beziehungsweise Phosphorsäureestern, ebenso von Verbindungen mit länger oder kürzerkettigen Alkylresten. Alternativ erfolgt auch ein Einsatz nur teilweise fluorierter oder nicht fluorierter Alkylketten. Neben der nachträglichen Imprägnierung mit dem jeweiligen Elektrolyten ist auch die Zugabe der Flüssigelektrolyte direkt in die Ziehlösung der Membran, oder bereits in die Polymerisationslösung bei der Herstellung der Polymere Bestandteil der Erfindung.
• 2. BZ MEA (Membran-Elektrodeneinheit) basierend auf einer Membran gemäß Punkt 1, bei der die betreffende Elektrode mit dem entsprechenden Elektrolyt getränkt oder an der aktiven Außenseite beschichtet wird.
• 3. BZ MEA (Membran-Elektrodeneinheit) bei der nur die Elektrode mit einem Elektrolyten gemäß Punkt 1 imprägniert bzw. an der Außenseite beschichtet wird, während die Membran mit davon abweichenden Flüssigelektrolyten, zum Beispiel H₃PO₄ imprägniert wird. Alternativ ist auch die Mischung einer der unter den Strukturen a) bis n), insbesondere der Verbindungen (1) bis (13), vorzugsweise (1) bis (8), aufgeführten Verbindungen, bzw. deren Derivate untereinander oder als Additiv zu einer anderen Protonensäure, zum Beispiel H₃PO₄, Bestandteil der Erfindung.
• 4. BZ MEA (Membran-Elektrodeneinheit) basierend auf einer Membran gemäß Punkt 1 bei der die Elektrolyt-/Säureaufnahme der Membran ausschließlich über die zuvor imprägnierte Elektrode in einem geeigneten Temperschritt erfolgt. Die Einbringung flüssiger Elektrolyte in die Elektrode geschieht dabei bevorzugt im Vakuum, etwa durch einen mehrfachen Belüftungs-/Entlüftungszyklus bei dem verbleibende Luftreste innerhalb der Elektrode graduell durch Flüssigelektrolyt ausgetauscht werden, möglich ist auch die Aufbringung des Elektrolyten auf eine Elektrode, die das betreffende Polymer bereits als Binder enthält. Zum Beispiel kann die Aufbringung über ein Airbrushverfahren erfolgen. Alternativ kann eine durch Heißpressen erhaltene MEA nachträglich als Ganzes in den Flüssigelektrolyt zur Imprägnierung eingelegt werden.
• 5. Brennstoffzellenmembran, die durch Imprägnierung einer porösen Membranmatrix mit den bevorzugten Verbindungen a) bis n), insbesondere der Strukturen (1) bis (13) erhalten wird. Je nach Aggregatszustand kann die Verbindung direkt in die Matrix eingebunden werden, oder muss erst in eine Lösung überführt werden (siehe Beispiele). Bei den porösen Trägern handelt es sich zum Beispiel um PTFE oder PET basierende Systeme unterschiedlicher Porosität (siehe zum Beispiel WO 01/93362 A , WO 03/63266 A , US 6299653 A , EP 309259 81 ) oder um oxidische, bevorzugt nanopartikulär beschichtete Systeme wie zum Beispiel: Al₂O₃/SiO₂ beschichtetes PET (zum Beispiel gemäß WO 02/47802 A1 ).
• 6. BZ MEA, bei der eine spezielle Anpassung der Elektroden an eine der Punkte 1 und 5 entsprechende Membran dadurch erreicht wird, dass die Elektroden auf der zur Membran hin weisenden Seite direkt mit Flüssigelektrolyt getränkt oder beschichtet bzw. mit einer Lösung des elektrolytbildenden Polymers in einem verdampfbaren organischen Lösungsmittel beschichtet werden. Diese Beschichtung ermöglicht bevorzugt im Zuge eines Heißpressvorganges eine gleichmäßige Anbindung der Elektrode an die Membran. Die Aufbringung des Elektrolyten auf die äußere Elektrodenoberfläche erfolgt zum Beispiel durch Aufstreichen mit einem Pinsel oder durch Besprühen über ein Airbrush-System.
• 7. Speziell auf den Membrantyp angepasste Elektrode, die einen geeigneten Anteil eines Polymerelektrolyten vorzugsweise gemäß Strukturen (9) bis (13) als Binder enthält. Die Materialien der Elektrode sind dabei bevorzugt für die Betriebstemperaturen der Membran optimiert.
• 8. Protonenleitende Membran gemäß der Punkte 1 und 5, wobei eine der bevorzugten Verbindungen a) bis n) [(1) bis (13), bevorzugt 1–8] als Zusatz (Additiv) zu einer weiteren protonenleitenden Säure, zum Beispiel Phosphorsäure verwendet wird, alternativ kann das Additiv auch nur im Bereich der Elektrode zugegeben werden. Das Additiv dient insbesondere der Reduzierung der Kathodenverluste (siehe zum Beispiel DE 10235358 A1 ).
• 9. Verwendung der erfindungsgemäßen Membran/MEA als protonenleitende Membran in einer Brennstoffzelle.
• 10. Verwendung einer erfindungsgemäßen Membran und MEA in einer Brennstoffzelle für Fahrzeuganwendungen (zum Beispiel APU + Traktion) und für stationäre Anwendungen (zum Beispie mobiles Kleinkraftwerk oder Hausenergieversorgung).

The invention is preferably realized as follows:

• 1. Use of compounds having the structures a) to n) [in particular compounds (1) to (13), preferably (1) to (8)], as impregnating agent in fuel cell membranes based on the impregnation of a shelf-basic polymer ( for example PBI) with liquid electrolyte (according to WO 96/13872 A . US 5525436 A . US 5716727 A . US 6025085 A . US 5599639 A . WO 99/04445 A . EP 983134 B1 . WO 01/18894 A . EP 954544 A1 and WO 01/18894 A2 . US 6124060 A ). Optionally, there is also a use of corresponding di- or triphosphonic acids and sulfonic acids, or phosphoric acid esters, as well as compounds with longer or shorter-chain alkyl radicals. Alternatively, only partially fluorinated or non-fluorinated alkyl chains are used. In addition to the subsequent impregnation with the respective electrolyte, the addition of the liquid electrolytes directly into the drawing solution of the membrane or already into the polymerization solution in the preparation of the polymers is also part of the invention.
• 2. BZ MEA (membrane electrode assembly) based on a membrane according to item 1, in which the relevant electrode is soaked with the corresponding electrolyte or coated on the active outer side.
• 3. BZ MEA (membrane electrode assembly) in which only the electrode is impregnated with an electrolyte according to item 1 or coated on the outside, while the membrane is impregnated with deviating liquid electrolytes, for example H ₃ PO ₄ . Alternatively, the mixture of one of the structures listed under the structures a) to n), in particular the compounds (1) to (13), preferably (1) to (8), or their derivatives with each other or as an additive to another Proton acid, for example H ₃ PO ₄ , part of the invention.
• 4. BZ MEA (membrane electrode assembly) based on a membrane according to item 1 in which the electrolyte / acid uptake of the membrane exclusively via the previously impregnated electrode in a suitable annealing step. The introduction of liquid electrolytes into the electrode is preferably done in a vacuum, such as by a multiple aeration / deaeration cycle in the remaining air residues within the electrode are gradually replaced by liquid electrolyte, is also possible the application of the electrolyte to an electrode, the polymer in question already contains as binder. For example, the application can be carried out via an airbrush method. Alternatively, an MEA obtained by hot pressing may be subsequently inserted as a whole in the liquid electrolyte for impregnation.
• 5. Fuel cell membrane, which is obtained by impregnation of a porous membrane matrix with the preferred compounds a) to n), in particular the structures (1) to (13). Depending on the state of the aggregate, the compound can be integrated directly into the matrix, or must first be converted into a solution (see examples). The porous supports are, for example, PTFE or PET based systems of different porosity (see for example WO 01/93362 A . WO 03/63266 A . US 6299653 A . EP 309259 81 ) or oxidic, preferably nanoparticulate coated systems such as: Al ₂ O ₃ / SiO ₂ coated PET (for example according to WO 02/47802 A1 ).
• 6. BZ MEA, in which a special adaptation of the electrodes to one of the points 1 and 5 corresponding membrane is achieved in that the electrodes soaked on the side facing the membrane directly with liquid electrolyte or coated or with a solution of the electrolyte-forming polymer in a vaporizable organic solvent. This coating preferably allows a uniform connection of the electrode to the membrane in the course of a hot pressing process. The application of the electrolyte to the outer electrode surface is carried out, for example, by painting with a brush or by spraying over an airbrush system.
• 7. Especially adapted to the membrane type electrode containing a suitable proportion of a polymer electrolyte preferably according to structures (9) to (13) as a binder. The materials of the electrode are preferably optimized for the operating temperatures of the membrane.
• 8. A proton-conducting membrane according to items 1 and 5, wherein one of the preferred compounds a) to n) [(1) to (13), preferably 1-8] is used as additive (additive) to a further proton-conducting acid, for example phosphoric acid Alternatively, the additive can be added only in the region of the electrode. The additive serves in particular to reduce the cathode losses (see for example DE 10235358 A1 ).
• 9. Use of the membrane / MEA according to the invention as a proton-conducting membrane in a fuel cell.
• 10. Use of a membrane according to the invention and MEA in a fuel cell for vehicle applications (for example, APU + traction) and for stationary applications (for example, mobile small power plant or domestic energy supply).

in the The invention is explained in more detail below with reference to examples, without that they are limited to shall be.

Examples for the Preparation of proton-conducting membranes using the preferred structures a) to n), in particular compounds (1) to (13).

Example 1:

Preparation of a solution of compounds 1 to 13:

To Weigh a suitable amount of each compound into a 100 ml beaker is carefully stirred with a magnetic stirrer 50 ml of a solvent, for example, acetone, acetonitrile, dimethoxyethane, ethanol, isopropanol added. Depending on the type of compounds used for the solution process higher Temperatures in the range up to 120 ° C (possibly also above) applied. In the used liquid Electrolytes become higher Loading achieved when previously diluted with a solvent will be produced.

Example 2:

Selection of suitable porous substrates:

Suitable are PTFE films such as those offered by the companies Bohlender, Exxon, Porex and BHA. Alternatively, oxidic, preferably nanoparticulate coated systems such as Al ₂ O ₃ / SiO ₂ coated PET from Creavis be used. The selection of the porous carrier takes place depending on the type of electrolytes used. For hydrophilic electrolytes, the oxidic supports are preferably used, for electrolytes with long, preferably fluorinated alkyl chains, the hydrophobic PTFE films. In order to prevent a discharge of the electrolytes by liquid water, preferably hydrophobic support materials are used for the fuel cell application. The pore radii of the support materials used are between 10 and 150,000 nm. The thickness of the support materials between 2 and 600 microns. The porosity is at least 10%.

Example 3:

Introduction of the polymer solutions in the porous ones Support materials:

• 3.1. Aufbringen der Lösung von oben auf das Vlies mit einer Pipette, bevorzugt befindet sich das poröse Vlies dabei auf einer von unten evakuierten Filtertritte. Alternativ kann die Lösung auch mit einer Airbrushpistole auf den Träger aufgebracht werden.
• 3.2. Einbringen der Lösung durch einen Evakuierungs-/Belüftungszyklus. Die Versuchsdurchführung wird dabei bevorzugt-in einem Aufbau gemäß 1 durchgeführt, die Probe befindet sich dabei in einem Vorlagegefäß, die aufzubringende Lösung in einem Vorratskolben. Über eine Verbindung mit einer Pumpe und zwei Hähnen kann die Probe wechselnd evakuiert werden, anschließend mit der Lösung beauftragt, belüftet und erneut evakuiert werden, so dass alle verbleibenden Gasrückstände in den Poren allmählich entfernt werden können.
• 3.3. Eine wiederum über einen massiven Rahmen stabilisierte poröse Folie wird in einer entsprechend konzentrierten Lösung des jeweiligen Elektrolyten in einem Hochdruckautoklaven mehrere Stunden mit Ar beauftragt (im Versuch mindestens bis 800 bar). Der Vorgang wird nach Ablassen des Druckes mehrmals wiederholt, bis eine genügend hohe Beladung des porösen Trägers mit der Elektrolytlösung sichergestellt ist.

The solution or the pure liquid electrolyte is introduced in various ways in the porous support materials described under 2. In particular, a uniform enforcement of all pores is necessary, so that the resulting membrane is subsequently gas-tight. The support material is preferably clamped to support on a solid support, for example made of PTFE or PP. Depending on the degree of wetting achieved, the processes described must be repeated several times in order to arrive at a complete gas-tightness of the porous membrane film.

• 3.1. Applying the solution from the top of the nonwoven with a pipette, preferably the porous web is on a bottom of the filter evacuated filter. Alternatively, the solution can also be applied to the carrier with an airbrush gun.
• 3.2. Introduce the solution through an evacuation / aeration cycle. The experimental procedure is preferred-in a structure according to 1 carried out, the sample is in a storage vessel, the solution to be applied in a storage flask. Through a connection with a pump and two taps, the sample can be alternately evacuated, then commissioned with the solution, aerated and evacuated again, so that all remaining gas residues in the pores can be gradually removed.
• 3.3. In turn, a porous film stabilized over a solid frame is charged with Ar in a correspondingly concentrated solution of the respective electrolyte in a high-pressure autoclave for several hours (at least up to 800 bar in the experiment). The process is repeated several times after releasing the pressure until a sufficiently high loading of the porous support with the electrolyte solution is ensured.

For each one Compounds 1 to 13 will be one for each Method 3.1. to 3.3. appropriate combination of solvent and suitable porous carrier determined professionally, allowing optimal wetting, full penetration of the porous support and even drying without Bubble formation possible is. At the undiluted liquid Electrolytes can be introduced directly into the carrier without solvent respectively.

The determination of the electrolyte uptake is based on the weight difference of the porous supports before and after the loading tests after removal of the solvent according to FIG. 4. In addition, the degree of the Hydrogen permeation before and after loading determined as a criterion for the effectiveness of the loading (Example 7). The degree of penetration of the polymer solution into the film is determined by means of scanning electron microscopy on sections of the films.

Example 4:

distance of the solvent after introduction into the porous Carrier: The impregnated after 3 porous carrier is transferred to a vacuum oven and there to remove the solvent carefully evacuated. Depending on the boiling point and decomposition temperature of the respective electrolyte may be used for drying a certain Temperature not exceeded become. To avoid blistering, it is necessary to slowly lower the pressure and to raise the temperature very slowly. The required drying time up to constant weight is usually at least 10 h.

It may prove positive, the resulting proton-conducting membrane while to press the drying phase between two heated flat sheets. proven have pressing pressures of at least 5 bar. After drying, the membranes become Determination of electrolyte absorption weighed.

Example 5:

Solvent-free Production process of membranes by hot pressing: The process is in particular for the production of films (polymer compacts) slightly soluble Polymer electrolytes suitable. It is the admission of a support film (PTFE / PP) with powdered polymer electrolyte and hot pressing between steel jaws (pressing pressure> 5 bar, temperature> 120 ° C). To Removal of the film gives a transparent film. alternative gets into the powder in the hot pressing process a porous one carrier according to example 2 introduced. For this purpose, the porous support is placed on a powder layer placed on top and also covered with powder from above. The thus obtained Sandwich will follow also hot pressed under the conditions described above. The membranes thus obtained are suitable for evaluating the conductivity novel polymer electrolytes.

Example 6:

Determination of proton conductivity:

The obtained by the above methods samples are in a heatable and humidity controllable conductivity cell between electrically conductive Carbon fleeces or gold platelets clamped. Subsequently, will the conductivity of the samples in the temperature range between room temperature and 160 ° C with help of impedance spectroscopy.

Example 7:

execution the hydrogen permeation measurements:

The volumetric flow is determined by means of a sample disk having a surface area of 2 cm ² by applying a hydrogen overpressure. Determination of flow (m1 / (cm ² * min.) After loading with the electrolyte.

Claims (23)

Use of ionic liquids based on fluorinated or partially fluorinated alkylphosphorus - / - phosphine or -phosphonic or alkylsulfonic acids or on the basis of derivatives of these, including derivatives and triacids as electrolytes for the production of fuel cell membranes or of fuel cell membrane electrode assemblies (MEA). Use according to claim 1, characterized in that the ionic liquid has at least one perfluoroalkyl group (C _n F _{2n + 1} ), where n = 1 to 8. Use according to claim 2, characterized the at least one perfuoroalkyl group is a trifluoromethyl group or pentafluoroethyl group. Use according to one of claims 1 to 3, characterized in that ionic liquids are used which comprise the following compounds individually, mixed with one another, in compositions or with other liquid electrolytes known per se: a) perfluoroalkyl phosphoric acid hydrate H ⁺ [(C _n F _{2n + 1} ) _6-z PF _z ] .yH ₂ O with n = 1 to 8, 2 ≦ z ≦ 5, y ≥ 3 b) perfluoroalkyl phosphoric acid in diethyl ether H ⁺ [(C _n F _{2n + 1} ) _6-z PF _z ] x y (C ₂ H ₅ ) ₂ O with n = 1 to 8, 2 ≦ z ≦ 5, y ≥ 2 c) bis (perfluoroalkyl) phosphinic acid (C _n F _{2n + 1} ) ₂ P (O) (OH) with n = 1 to 8 d) perfluoroalkylphosphonic acid (C _n F _{2n + 1} ) P (O) (OH) ₂ with n = 1 to 8 e) fluorinated or partially fluorinated alkylsulfonic acids (C _n F _{2n + 1-t} H _t ) SO ₃ H with n = 1 to 8 and t = 0 to 4; at n = 1, t = 0 to 2. Use according to claim 4, characterized in that ionic liquids are used which comprise the following compositions: f) Compositions 1,1-dimethylpyrrolidinium bis (perfluoroalkyl) phosphinate: bis (perfluoroalkyl) phosphinic acid (1: 1 w / w) and 1 , 1-dimethylpyrrolidinium perfluoroalkylphosphonate: perfluoroalkylphosphonic acid, wherein the perfluoroalkyl group has (C _n F _{2n + 1} ) n = 1 to 8, g) composition [1,1-dimethylpyrrolidinium-perfluoroalkylfluorophosphate]: [triethylene glycol dimethyl ether perfluoroalkylfluorophosphoric acid complex; (1: 1 w / w)

where n and z have the meanings mentioned under claim 4; optionally in combination with phosphonic acid / H ₃ PO ₄ : h) Composition [1,1-dimethylpyrrolidinium-perfluoroalkyifluorophosphate]: [Polyethylene glycol 200-trisperfluoroalkylfluorophosphorous acid complex; (1: 1 w / w)

where n and z have the meanings mentioned under claim 4; optionally in combination with phosphonic acid / H ₃ PO ₄ ; i) guanidinium perfluoroalkyl fluorophosphate [(R ₂ N) ₃ C] ⁺ [(C _n F _{2n + 1} ) _6-z PF _z ] wherein R = H and / or C ₁ -C ₈ alkyl, and n and z have the meanings mentioned under claim 4; j) Protonated polyethyleneimine (one proton per unit) in combination with a compound a) to e) according to claim 4 and / or H ₃ PO ₄ and their derivatives, preferably

where R = H and / or C ₁ -C ₄ alkyl; n and z have the meanings mentioned under claim 4; k) Protonated polyethyleneimine (two protons per unit) in combination with a compound a) to e) according to claim 4 and / or H ₃ PO ₄ and their derivatives, preferably the compound

where R = H and / or C ₁ -C ₄ alkyl; n and z have the meanings mentioned under claim 4; l) Protonated polyethylene glycol in combination with a compound a) to e) according to claim 4 and / or H ₃ PO ₄ and their derivatives, preferably the compound

where R = H and / or C ₁ -C ₄ alkyl; n and z have the meanings mentioned under claim 4; m) Alkylated poly (melamine-co-formaldehyde) in combination with a compound a) to e) according to claim 4 and / or H ₃ PO ₄ and derivatives thereof, preferably as di- [perfluoroalkylfluorophosphate]

where R = H and / or C ₁ -C ₄ alkyl; n and z have the meanings mentioned under claim 4; n) poly [N, N'-bis (2,2,6,6-tetramethyl-4-piperidinyl) -α, ω-diamine-CO-2,4-dichloro-6-morpholino-1,3,5- triazine] in combination with a compound a) to e) according to claim 4 and / or H ₃ PO ₄ and derivatives thereof, preferably as pentaperfluoroalkylfluorophosphate)]

where R = H and / or C ₁ -C ₄ alkyl; n and z have the meanings mentioned under claim 4; Use according to one or more of claims 1 to 5, characterized in that the compounds for impregnation of preferably basic polymers or polymer matrices used become. Use according to claim 6, characterized that the basic polymer is selected is made of polybenzimidazole (PBI), a poly (pyridine), a poly (pyrimidine), a polyimidazole, a polybenzothiazole, a polybenzoxazole, a polyoxadiazole, a polyquinoxaline, a polythiadiazole and a poly (tetrazapyren). Use according to one or more of claims 1 to 7, characterized in that the compounds optionally in combination with the basic polymers with per se known Polymer membrane matrices are used, if necessary already with other liquid electrolytes, preferably phosphoric acid, waterproof are. Use according to one or more of claims 1 to 8, characterized in that they are for subsequent impregnation be used by membranes or directly in the solution at the production of membranes or directly in the polymerization solution. Use according to one or more of claims 1 to 9 for obtaining fuel cell membranes, characterized that porous Membrane matrices with the electrolyte directly or in a solution in an organic solvent be treated and the solvent subsequently is evaporated and after evaporation preferably a self-supporting Film forms. Use according to claim 10, characterized that as porous Membrane matrices on polytetrafluoroethylene (PTFE), polypropylene (PP) and / or polyethylene terephthalate (PET) based systems or oxidic, preferably nanoparticulate coated systems are used. Use according to claim 10 or 11, characterized that a porous one Fleece acts as a porous support, which is located on a filter frit evacuated from below, on which the compounds according to a the claims 1 to 5 are applied. Use according to claim 10 or 11, characterized that compounds onto a porous support through an evacuation / aeration cycle are introduced, with a membrane sample alternately alternating evacuated and with a solution the compounds according to a the claims 1 to 5, so that all gas residues in the pores are removed. Use according to claim 10 or 11, characterized that one over a frame stabilized porous Matrix with the compounds according to a the claims 1 to 5 in a concentrated solution in a high pressure autoclave is commissioned several times. Use according to one or more of claims 1 to 5, characterized in that the compounds for the preparation an MEA used to coat or soak the electrode become. Use according to claim 15, characterized that the ionic liquids directly for insertion into the electrode on the to a membrane indicative page can be used or in a solution to Painting, spraying or with a vaporizable solvent for coating the electrode, preferably in the course of a hot pressing operation. Use according to one or more of claims 1 to 16 for obtaining a fuel cell membrane electrode unit (BZ MEA), characterized in that either the electrode is an ionic liquid according to one the claims 1 to 5 and / or the membrane, optionally in combination with a Proton acid, preferably phosphoric acid, which are combined with both the electrode and the membrane can. Use according to claim 17, characterized that an electrode, the ionic liquid according to a the claims 1 to 5 as a binder or that the electrode on the catalyst side with the ionic liquid is coated. Use according to one or more of claims 1 to 18, characterized in that the introduction of the electrolytes in a vacuum. Use according to one or more of claims 1 to 19, characterized in that the introduction of the electrolytes at higher Temperatures are. Use according to one or more of claims 1 to 20, characterized in that the compounds as an additive to known protonic acids, preferably phosphoric acid, be used. Fuel cell for vehicle applications and stationary applications comprising a membrane or MEA according to one or more of claims 1 to 21st Ionic liquids and their derivatives having the following compositions: - 1,1-dimethylpyrrolidinium bis (perfluoroalkyl) phosphinate: bis (perfluoroalkyl) phosphinic acid (1: 1 w / w) - 1,1-dimethylpyrrolidinium perfluoroalkylphosphonate: perfluoroalkylphosphonic acid (1: 1 w / w), wherein the perfluoroalkyl group has (C _n F _{2n + 1} ) n = 1 to 8, - [1,1-dimethylpyrrolidinium perfluoroalkylfluorophosphate]: [triethylene glycol dimethyl ether perfluoroalkylfluorophosphoric acid complex] (1: 1 w / w) - [1, 1-dimethylpyrrolidinium-perfluoroalkylfluorophosphate]: [polyethyleneglycol-200-trisperfluoroalkylfluorophosphoric acid complex]; (1: 1 w / w) - Protonated polyethyleneimine (one proton per unit) in combination with one of the compounds a) to e) according to claim 4, - Protonated polyethyleneimine (two protons per unit) in combination with one of the compounds a) to e) according to claim 4, - Protonated polyethylene glycol in combination with one of the compounds a) to e) according to claim 4, - Alkylated poly (melamine-co-formaldehyde) in combination with one of the compounds a) to e) according to claim 4, preferably the di- [perfluoroalkylfluorophosphate] - poly [N, N'-bis (2,2,6,6-tetramethyl-4-piperidinyl) -α, ω-diamine-CO-2,4-dichloro-6-morpholino-1 , 3,5-triazine] in combination with one of the compounds a) to e) according to claim 4, preferably the penta [perfluoroalkylfluorophosphate] and their combinations with other acids, preferably with H ₃ PO ₄ .