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WO2005020362A1 - Electrolytes en polymere composite pour piles a combustibles a membrane echangeuse de protons - Google Patents

Electrolytes en polymere composite pour piles a combustibles a membrane echangeuse de protons Download PDF

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Publication number
WO2005020362A1
WO2005020362A1 PCT/US2004/001960 US2004001960W WO2005020362A1 WO 2005020362 A1 WO2005020362 A1 WO 2005020362A1 US 2004001960 W US2004001960 W US 2004001960W WO 2005020362 A1 WO2005020362 A1 WO 2005020362A1
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WIPO (PCT)
Prior art keywords
composite electrolyte
based material
polymer
silica
cation exchange
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PCT/US2004/001960
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English (en)
Inventor
Karl Taft
Matthew Robert Kurano
Arunachaka Nadar Mada Kannan
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Hoku Scientific, Inc.
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Publication date
Priority claimed from PCT/US2002/039104 external-priority patent/WO2004015801A1/fr
Application filed by Hoku Scientific, Inc. filed Critical Hoku Scientific, Inc.
Priority to EP04704918A priority Critical patent/EP1665438A1/fr
Priority to JP2006523816A priority patent/JP2007503089A/ja
Publication of WO2005020362A1 publication Critical patent/WO2005020362A1/fr

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
    • B01D67/0079—Manufacture of membranes comprising organic and inorganic components
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/02—Inorganic material
    • B01D71/024—Oxides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/02—Inorganic material
    • B01D71/028—Molecular sieves
    • B01D71/0281—Zeolites
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/52—Polyethers
    • B01D71/521—Aliphatic polyethers
    • B01D71/5211—Polyethylene glycol or polyethyleneoxide
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/52—Polyethers
    • B01D71/522—Aromatic polyethers
    • B01D71/5221—Polyaryletherketone
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/52—Polyethers
    • B01D71/522—Aromatic polyethers
    • B01D71/5222—Polyetherketone, polyetheretherketone, or polyaryletherketone
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F283/00—Macromolecular compounds obtained by polymerising monomers on to polymers provided for in subclass C08G
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L55/00—Compositions of homopolymers or copolymers, obtained by polymerisation reactions only involving carbon-to-carbon unsaturated bonds, not provided for in groups C08L23/00 - C08L53/00
    • C08L55/02—ABS [Acrylonitrile-Butadiene-Styrene] polymers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/10—Fuel cells with solid electrolytes
    • H01M8/1016—Fuel cells with solid electrolytes characterised by the electrolyte material
    • H01M8/1018—Polymeric electrolyte materials
    • H01M8/102—Polymeric electrolyte materials characterised by the chemical structure of the main chain of the ion-conducting polymer
    • H01M8/1025—Polymeric electrolyte materials characterised by the chemical structure of the main chain of the ion-conducting polymer having only carbon and oxygen, e.g. polyethers, sulfonated polyetheretherketones [S-PEEK], sulfonated polysaccharides, sulfonated celluloses or sulfonated polyesters
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/10—Fuel cells with solid electrolytes
    • H01M8/1016—Fuel cells with solid electrolytes characterised by the electrolyte material
    • H01M8/1018—Polymeric electrolyte materials
    • H01M8/1041—Polymer electrolyte composites, mixtures or blends
    • H01M8/1046—Mixtures of at least one polymer and at least one additive
    • H01M8/1051—Non-ion-conducting additives, e.g. stabilisers, SiO2 or ZrO2
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/10—Fuel cells with solid electrolytes
    • H01M8/1016—Fuel cells with solid electrolytes characterised by the electrolyte material
    • H01M8/1018—Polymeric electrolyte materials
    • H01M8/1069—Polymeric electrolyte materials characterised by the manufacturing processes
    • H01M8/1081—Polymeric electrolyte materials characterised by the manufacturing processes starting from solutions, dispersions or slurries exclusively of polymers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/02—Inorganic material
    • B01D71/024—Oxides
    • B01D71/027—Silicium oxide
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0065—Solid electrolytes
    • H01M2300/0068—Solid electrolytes inorganic
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0088—Composites
    • H01M2300/0091—Composites in the form of mixtures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04082—Arrangements for control of reactant parameters, e.g. pressure or concentration
    • H01M8/04197—Preventing means for fuel crossover
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/10—Fuel cells with solid electrolytes
    • H01M8/1009—Fuel cells with solid electrolytes with one of the reactants being liquid, solid or liquid-charged
    • H01M8/1011—Direct alcohol fuel cells [DAFC], e.g. direct methanol fuel cells [DMFC]
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present invention relates to proton conducting composite polymer membranes providing one or more of the following: a functionalized polymer and one or more clay based cation exchange material.
  • the composite polymer membranes can be used as proton conducting electrolytes in hydrogen oxygen fuel cells, proton exchange fuel cells (PEMFC) or direct methanol fuel cells (DMFC). These composite polymer membranes exhibit improvement in ion exchange capacity (IEC), proton conductivity, water uptake, oxidative resistance, thermal stability and mechanical strength.
  • IEC ion exchange capacity
  • Fuel cells have been long considered a promising solution for the production of clean and efficient energy.
  • the electrochemical conversion that takes place in fuel cells is not limited by the Carnot efficiency which restricts the efficiencies of internal combustion engines (ICE).
  • ICE internal combustion engines
  • a fuel cell is two or three times more efficient than ICEs converting fuel to power.
  • fuel cells offer the advantage of continuous power as long as the reactant fuel and oxidant are supplied. This eliminates the time consuming procedure of recharging.
  • fuel cells are environmentally friendly.
  • a metal catalyst oxidizes the hydrogen gas into protons and electrons . Then, water is the only emission when hydrogen is used as the fuel.
  • the electrode assemblies of both the anode and the cathode contain a metal catalyst (e.g., platinum) supported by a conductive material.
  • a metal catalyst e.g., platinum
  • Some PEM fuel cells use a diffusion layer on both electrodes to help distribute gases evenly across the electrode surfaces.
  • Fuel cells use an electrolyte between the cathode (positive electrode) and the anode (negative electrode). Fuel cells employing proton conducting electrolyte membranes are referred to as "proton exchange membrane fuel cells" (PEMFC).
  • PEM fuel cells produce electricity, water, and heat.
  • PEM fuel cells can also operate with fuels such as methanol. In this case, methanol is introduced directly onto the anode compartment and is internally reformed.
  • PEMFC direct methanol fuel cells
  • DMFC direct methanol fuel cells
  • PEMFC and DMFC are the preferred power sources for residential, portable, and transport applications, due to their relatively lower operation temperature.
  • Both PEMFCs and DMFCs use a proton conducting membrane as the electrolyte and composite electrode assemblies consisting of platinum based electrocatalysts and carbon.
  • the main difference between PEMFCs and DMFCs is the type of fuel each of them uses and their emissions. While PEMFC uses gaseous hydrogen as fuel and emits only water, DMFC uses methanol as fuel and emits water and carbon dioxide.
  • PEMFC proton exchange membrane
  • proton exchange membranes act as an ionic conductor between anode and cathode and also separate the fuel and oxidant.
  • polymer electrolyte membranes are being explored as proton exchange membranes in PEM fuel cells.
  • PEMFC and DMFC use expensive hydrated perfluorosulfomc acid based membranes as the electrolyte due to their excellent chemical, mechanical and thermal stability and relatively high proton conductivity of around 0.08 Scm "1 in the hydrated state.
  • Nafion® Nafion® is a trademark of
  • Nafion ® which is described, for example, in U.S. Patent No. 4,330,654 is fabricated by melting tetrafuoroethylene and perfluorovinyl ethersulfonyl fluoride together, shaping the mixture, and then hydrolyzing the melt to yield the ionic sulfonate form.
  • perfluorinated ionomer membranes such as Nafion ® membranes, are effective in PEM fuel cells they have limitations. Among these limitations are high osmotic swelling, high methanol permeability, reduced proton conductivity at elevated temperatures (> 80°C), and high cost.
  • these membranes need to be humidified adequately to provide satisfactory proton conductivity. This is due to the hydrophilic nature of the sulfonic acid groups attached to the polymer backbone and the necessity to hydrate the ionic clusters.
  • the membrane temperature exceeds the boiling point of water, the membrane dehydrates and experiences a dramatic decrease in the proton conductivity. Consequently, perfluorinated ionomer membranes, such as Nafion® membranes, are not regarded as suitable for fuel cell applications above 100 °C.
  • operation of the PEMFC at elevated temperatures T > 100 °C
  • the higher operating temperature can provide faster reaction kinetics and better efficiency, reduce or eliminate the poisoning of the Pt-based catalysts by carbon monoxide impurity in the fuel, and possibly allow the use of less expensive non-platinum alloy or transition metal oxide catalysts.
  • high methanol permeability is another significant deficiency exhibited by perfluorinated ionomer membranes (e.g., Nafion® membranes). Methanol crossover is much more prevalent than hydrogen crossover, especially at concentrations above 10 wt%. This is primarily due to the liquid concentration gradient. To minimize crossover, some researchers have incorporated additives into Nafion® or vaporized methanol before introducing it to the anode side of the cell.
  • Nafion® perflouronated membranes
  • Nafion® is high cost ($700 per square meter at the time of this writing). Due to its relatively complicated and time-consuming manufacturing process, Nafion ® is indeed very expensive. A square meter of Nafion ® is known to cost approximately $700.
  • Nafion® membranes represent 10 to 15% of the total cost of a single PEM fuel cell or stack of fuel cells. It is generally accepted that if Nafion ® were to continue to represent the leading membrane candidate for PEM fuel cells, its cost must come down substantially before these cells can become competitive in the fuel cell market.
  • Nafion® is also limited to operating temperatures below 90°C. High temperatures lead to lower proton conductivity due to dehydration and degradation.
  • sol-gel and other processes to infiltrate the porous structure of Nafion® with components that will increase its performance at elevated temperatures.
  • Staiti et al and Tazi et al impregnated Nafion® with phosphotungstic acid and silicotungstic acid/thiophene, respectively, which increased proton conductivity and hydration levels at temperatures up to 120 °C. (See, P.
  • a variety of alternative membranes have been considered for solving the technical limitations of Nafion® in PEM fuel cells, but none of these alternatives has demonstrated sufficient advantages to replace Nafion® as the membrane of choice.
  • One alternative membrane incorporates Nafion® or a Nafion®-like polymer into a porous polytetrafluoroethylene (Teflon®) structure. These membranes are available under the trade name Gore-Select® from W. L. Gore & Associates, Inc. and they are described in U.S. Patent Nos. 5,635,041, 5,547,551 and 5,599,614. Other alternative membranes are available under the trade names Aciplex® from Asahi Chemical Co. and Flemion® from Asahi Glass.
  • Nafion® Due to their polyfluorinated structures, these alternative membranes exhibit many of the same deficiencies as Nafion®, namely, limited ionic conductivity at elevated temperatures, dehydration or drying up, and fuel crossover.
  • the main disadvantage of such membranes is that they loose some of the cross sectional area of the proton conductive material due to the presence of the inactive support.
  • Another alternative to Nafion® membrane employs polybenzimidazole polymers (PBI) that are infiltrated with phosphoric acid.
  • PBI polybenzimidazole polymers
  • the present invention is based, in part, on the discovery of composite electrolyte membranes that can be used as proton exchange membranes in PEM fuel cells, and the processes for producing these membranes.
  • One aspect of the invention is directed to a composite electrolyte for use in electrochemical fuel cell that includes: (i) an inorganic cation exchange material; (ii) a silica- based material; and (iii) a proton conducting polymer-based material.
  • the inorganic cation exchange material comprises about 0.1 wt% to about 99 wt%
  • the silica-based material comprises about 0 wt% to about 70 wt%
  • the proton conducting polymer-based material comprises about 0.1 wt% to 99.9 wt% of the composite electrolyte.
  • Preferred cation exchange materials include clays, zeolites, hydrous oxides, and inorganic salts.
  • the clay includes an aluminosilicate-based exchange material selected from the group consisting of montmorillonite, kaolinite, vermiculite, smectite, hectorite, mica, bentonite, nontronite, beidellite, volkonskoite, saponite, magadite, kenyaite, zeolite, alumina, rutile.
  • the clay is modified to make it more compatible with organic matrices, wherein a clay modification includes exfoliation which helps to separate platelets of inorganic substance.
  • Another aspect of the invention is directed to an electrochemical fuel cell that includes: (i) an anode; (ii) a cathode; (iii) fuel supply means for supplying fuel toward the anode; (iv) an oxidant supply means for supplying oxidant toward the cathode; and (v) a composite electrolyte positioned between the anode and cathode.
  • the composite electrolyte includes (a) an inorganic cation material, (b) a silica-based material, and (c) a polymer-based material, wherein the inorganic cation exchange material comprises about 0.1 wt% to about 99 wt%, the silica-based material comprises about 0 wt% to about 70 wt%, and the proton conducting polymer-based material comprises about 0.1 wt% to 99.9 wt% of the composite electrolyte.
  • Yet another aspect of the invention is directed to a method of fabricating a composite electrolyte for use in an electrochemical fuel cell.
  • the method includes (i) applying onto a surface of a substrate a viscous liquid composition of (a) an inorganic cation exchange material, (b) silica-based material, (c) a polymer-based material, and (d) a solvent-dispersant.
  • the method further includes (i) spreading the viscous liquid composition to form a uniform thickness layer on the substrate; and (ii) allowing the solvent to evaporate from the viscous liquid composition to yield the composite electrolyte.
  • the inorganic cation exchange material comprises about 0.1 wt% to about 99 wt%
  • the silica-based material comprises about 0.1 wt% to about 70 wt%
  • the polymer-based material comprises about 0.1 wt% to 99.9 wt% of the composite electrolyte.
  • Figure 1 illustrates operation of PEM fuel cell
  • Figures 1A & IB show an exemplary fuel cell with an embodiment of the composite electrolyte.
  • Figure 2 is a graph comparing IEC values of the present invention.
  • Figure 3 is a plot of proton conductivity in saturated water vapor of the present invention
  • Figure 4 is a plot of comparison of water retention characteristics of the present invention and Nafion®.
  • Figure 5 is a plot of tensile strength for the present invention.
  • Figure 6 is a plot of Young's modulus for the present invention.
  • Figure 7 is a plot comparing proton conductivity at various temperatures for the present invention.
  • Figure 8 is a plot comparing cell output performance for Nafion® membrane and a membrane constructed in accordance with principles of the present invention.
  • the present invention provides a low cost, composite membrane and a cost effective method for fabricating such membranes.
  • a composite membrane produced in accordance with the present invention exhibits properties comparable to Nafion® when used as an electrolyte in fuel cells.
  • a composite membrane provided in accordance with the present invention exhibits higher proton conductivity at elevated temperatures, greater mechanical strength, higher ion exchange capacity, and lower methanol crossover as compared to Nafion®.
  • This composite membrane is well suited for use as a proton exchange membrane in hydrogen-oxygen fuel cells and direct methanol fuel cells. It is noted that the composite membrane can be employed as an electrolyte in conventional fuel cells which are described, for example, in U.S. Patent No. 5,248,566 and 5,5477,77.
  • the electrochemical cell 10 generally includes a membrane electrode assembly (MEA) flanked by graphite based anode 12 and cathode 16 flow field structures.
  • MEA membrane electrode assembly
  • the external circuit can comprise any conventional electronic device or load such as those described in U.S. Patent Nos. 5,248,566, 5,272,017, 5,547,777 and 6,387,556.
  • the components, mainly the MEA assembly can be hermetically sealed by known techniques.
  • fuel 18 from fuel source diffuses through the anode 12 and an oxidizer 20 from oxidant source (e.g., container or ampoule) diffuses through the cathode 16 of the MEA.
  • oxidant source e.g., container or ampoule
  • the composite electrolyte (the composite membrane) 22 conducts ions between the anode 12 and cathode 16, separates between the fuel 18 and oxidant 20 and insulates between the cathode and anode so that the electrons current is conducted through the external circuit rather than the membrane.
  • Hydrogen oxygen fuel cells use hydrogen 18 as the fuel and oxygen 20 as the oxidizer.
  • the fuel is liquid methanol.
  • the fuel cell 10 includes a membrane electrode assembly 12 flanked by the anode and cathode structures, 36 and 38.
  • the cell On the anode side, the cell includes an endplate 14, graphite block or bipolar plate 18 with openings 22 to facilitate gas distribution, gasket 26, and anode carbon cloth current collector 30.
  • the cell On the cathode side, the cell includes stainless steel endplate 16, graphite block or bipolar plate 20 with openings 24 to facilitate gas distribution, gasket 28, and cathode carbon cloth current collector 32.
  • the carbon cloth material is a porous conductive substance.
  • the membrane electrode assembly (MEA) 12 includes a proton exchange membrane 46 that is flanked by anode 42 and cathode 44 electrodes. Each electrode is made of a porous electrode material such as carbon cloth or carbon paper.
  • the proton exchange membrane 46 fashioned as the inventive composite electrolyte, provides for ion transport during operation of the fuel cell.
  • the composite electrolyte comprises: (i) an inorganic cation exchange material, (ii) a silica-based material, and (iii) a polymer-based material. The invention allows, however, any combination of these materials to be used for producing a proton exchange membrane.
  • the preferred inorganic cation exchange materials include clays, zeolites, hydrous oxides, and inorganic salts, which are described, for example, in Amphlett, C.B., Inorganic Ion Exchangers, Elsevier Publishing Co., Amsterdam, 1964, and Qureshi et al, Inorganic Ion Exchangers in Chemical Analysis, CRC Press, Boca Raton, 2000.
  • Preferred zeolites include heulandite, analcite, chabazite, phillipsite, ZK5, ZK4, mordenite, and the linde family.
  • Preferred hydrous oxides include ferrous hydroxide, magnesium hydroxide, aluminum hydroxide, and beryllium oxide.
  • Preferred inorganic salts include zirconium phosphate, titanium phosphate, zirconium arsenate, tin phosphate, and cerium phosphate.
  • Preferred clays include aluminosilicate-based exchange materials selected from the group consisting of montmorillonite, kaolinite, vermiculite, smectite, hectorite, mica, bentonite, nontronite, beidellite, volkonskoite, saponite, magadite, kenyaite, zeolite, alumina, rutile, and mixtures thereof. These clays are commercially available. For example, montmorillonite is available from Aldrich Fine Chemicals. .
  • the clays can be tailored to make them more compatible with organic matrices. Modifications include, but are not limited to exfoliation which helps to separate the platelets of inorganic substance more effectively.
  • the composite electrolyte is comprised of about 0.1% to about 99% inorganic cation exchange material, and preferably about 0.1 % to about 30% (all percentages herein are based on weight unless otherwise noted).
  • the inorganic cation exchange materials serve a number of functions. Foremost, these materials help increase ion exchange capacity (IEC).
  • Figure 2 shows the IEC values for several membranes with different amounts of montmorillonite (MMT) and also with modified montmorillonite (mMMT).
  • Montmorillonite is just one of the clay materials that may be used solely or in combination with other additives.
  • the modified montmorillonite (Nanomer 1.24 TL, by Nanocor, Inc., Arlington Heights, IL) consists of montmorillonite treated with aminododecanoic acid.
  • Other possible modifiers of inorganics include trimethyl stearate ammonium (Nanomer, 1.28E, by Nanocor, Inc., Arlington Heights, IL), Octadecylamine (Nanomer, 1.30 E, by Nanocor, Inc., Arlington Heights, IL), methyl dihydroxy hydrogenated tallow ammonium (Nanomer, 1.34 TCN, Nanocor, Inc., Arlington Heights, IL), etc.
  • the layered structure of montmorillonite is created by strong electrostatic forces that hold the adjacent clay platelets together.
  • the aspect ratios of the stacked platelet structure are far greater than that of the individual platelets which are on the order of 100-1500 nm.
  • Nano-sized platets may increase the modulus of the matrix without a concomitant decrease in ductility; as is generally observed when micron-sized additives are used. Therefore, the benefit of using high aspect ratio platelets can be realized only if the stacks are separated, in order to evaluate the effect of additives on the IEC, the base proton conducting polymer is identical in all the cases.
  • Figure 2 illustrates the empirical results of proton conductivity at a particular temperature of 90 °C for various compositions of composite polymer electrolyte membranes. The two probe conductivity method for analyzing the proton conductivity of these same membranes is similar to a method described by Mueller and Urban. See Mueller et al.
  • the addition of the inorganic material significantly reduces water swelling.
  • the incorporation in the polymer of some of the inorganic materials as those disclosed here also improves the water retention capability of the membrane at elevated temperatures. This is critical to achieving adequate conductivities at elevated temperatures. What is significant is that the addition of montmorillonite helps the membrane to retain water at elevated temperatures with very low heating ramp. Due to its high conductivity at elevated temperatures and moisture retaining capabilities, the composite electrolyte membrane is expected to support fuel cell operations up to 120° C.
  • the addition of inorganic materials such as clays in the polymer matrix tends to increase the mechanical strength of the membrane.
  • the inorganic cation exchange materials disclosed in the present invention also tend to improve the structural integrity of the membrane, in particular, by reducing the degree of dimensional fluctuations caused by electrochemical cell temperature variations and/or variations in composite electrolyte membrane water content.
  • tensile strength more than doubles with the addition of inorganic cation exchange materials in either dry or wet conditions.
  • Figure 5 highlights the effect of inorganic cation exchange materials on tensile strength in both wet and dry conditions.
  • the dry modulus increases by approximately 10%.
  • the Young's modulus ( Figure 6) of the composite polymer electrolyte membrane is increased by about 20 %.
  • composite polymer membranes with unmodified montmorillonite show much higher tensile strength and young's modulus as compared to the pristine polymer membranes (membranes without additives).
  • the composite membranes using modified montmorillonite as an additive show even better mechanical behavior compared to the pristine and composite membranes with montmorillonite. This can be explained by the better exfoliation of the montmorillonite clay particles with high aspect ratios.
  • the silica-based material has many positive affects. These include increasing the IEC, increasing proton conductivity, reducing the swelling of hydrophilic materials, and increasing the mechanical strength.
  • Silica based materials increase the ion exchange capacity of the composuite membrane, especially when inorganic cation exchange materials are present.
  • the silica-based material is comprised of materials containing silica, silicates, and/or silicates having organic groups such as silicate esters or any combinations thereof.
  • Preferred silica-based materials include a colloidal silica comprising discrete spheres of silica that is available under the trade name LUDOX Aldrich Fine Chemicals.
  • Another preferred silica- based material is a silica based binder known by tetraethylorthosilicate (TEOS) also from Aldrich Fine Chemicals.
  • TEOS tetraethylorthosilicate
  • the composite electrolyte contains about 0.1% to about 70% and preferably from about 0.1% to about 30% of the silica-based material.
  • the addition of a silica-based material to kaolinite increases kaolinite 's cation exchange capacity by 200% .
  • the proton conductivity of the composite electrolyte membrane containing TEOS and kaolinite in the base polymer is greater than a membrane containing just kaolinite.
  • the proton conductivity of the composite electrolyte membrane containing TEOS and Clay (montmorillonite) in the polymer matrix is greater than a membrane containing just montmorillonite or TEOS, indicating that materials such as TEOS help improve membrane conductivity.
  • the polymer-based material is comprised of a polymer, or polymers that serve as the adhesive or base for the other components of the composite electrolyte. Any suitable polymer that is sufficiently chemically inert, mechanically durable, and ductile to withstand the operation conditions of electrochemical devices, particularly those of PEM fuel cells, can be employed.
  • the general polymer structure may be linear, branched, or a network or a combination thereof.
  • Preferred polymer materials include acrylonitrile/butadiene/stryene rubber (ABS), styrene butadiene/acrylate/acetate polymer blends, epoxides, and thermoplastics, or mixtures thereof.
  • Preferred thermoplastics include, but are not limited to, polypropylene, polycarbonate, polystyrene, polyethylene, polyaryl ether sulfones, poly aryl ether ketone, and polysulfones.
  • Particularly, preferred polymers have functional groups such as, sulfonate, phosphate, carbonate, amide, or imide groups, which have inherent proton conducting capabilities.
  • the polymer- based material besides increasing the mechanical strength of the composite electrolyte membrane, also increases the proton conductivity during electrochemical cell operation.
  • the composite electrolyte is comprised of about 0.1% to about 99.9% and preferably from about 40% to about 99.9% polymer-based material.
  • the composite electrolyte does not require perfluoronated polymers such as Nafion® or its derivatives.
  • the composite electrolyte can further include additives such as preservatives, thixotropy and viscosity control agents, crosslinking agents, conditioners, plasticizers, water control agents, proton conducting materials and other enhancing components commonly known in the art.
  • the dried composite electrolyte membrane consists essentially of three primary components, namely: (i) an inorganic cation exchange material, (ii) a silica- based material, and (iii) . a polymer-based material. Indeed, in preferred embodiments, the three primary components make up at least 90% of the solids of the composite electrolyte.
  • Figure 8 highlights the performance of an exemplary fuel cell with a particular composite membrane embodiment. It can be observed that the composite membrane with montmorillonite in accordance with the present invention performs better than Naifon ® (current density and power density) under identical operating conditions.
  • the composite electrolyte preferably has a proton conductivity on the order of 0.005 S/cm and more preferably of at least 0.05 S/cm below 100°C. This will enable the rapid proton transfer from anode to cathode when the composite electrolyte is used as a proton exchange membrane in a fuel cell.
  • the various attributes of a composite electrolyte in accordance with the present invention provide for better manufacturing results.
  • the composite membrane tends to be more physically robust to adequately withstand MEA manufacturing processes and pressure differentials within a fuel cell stack. Furthermore, the membrane tends to have a higher water retaining potential. This will enable higher temperature operation without sacrificing proton conductivity. Finally, the membrane tends to be more chemically robust so as not to degrade in the stack environment.
  • the composite membranes of the present invention can be fabricated by thoroughly mixing the membrane components in a solvent to minimize agglomeration. Water can be used as the solvent; raising the pH of the water on occasion helps to stabilize the particles in the slurry and facilitate mixing.
  • solvents such as, but not limited to, n-methyl pyrrilidione, dimethyl sulfone, dimehyl acidimide, and dimethyl formaldehyde may be used.
  • the viscous solution is poured over a substrate and leveled to a uniform thickness. After evaporation of the solvent and removal from the substrate, the membrane is cut to size and is ready for use. Heat, or reducing the pressure can be applied to facilitate evaporation.
  • a preferred technique is a tape casting method whereby the slurry of components is poured onto a silicon coated polyester (MYLAR) sheet.
  • a doctor blade moving across the slurry adjusts the height to the desired thickness ranging from about 0.5 ⁇ m to about 500 ⁇ m and preferably from about 100 ⁇ m to about 300 ⁇ m. Evaporation of the solvent takes place in a controlled temperature and humidity environment.
  • Other methods of membrane assembly include extrusion and tray casting.
  • the formulation involves adding a Montmorillonite or modified montmorillonite (1.24 TL, Nanomer, IL, USA) to different samples of sulfonated polyether ether ketone (SPEEK) to create membranes with 0, 3, 5, 7, 10 and 15 wt % loading of clay. SPEEK and clay mixtures are grounded to disperse the clay uniformly and aid in dissolution.
  • SPEEK sulfonated polyether ether ketone
  • the mixture of SPEEK and clay are dissolved in approximately 10 ml distilled N,N-dimethyl formaldehyde (DMF) by stirring for about 2 hours using a magnetic stir bar. Subsequently, the solution of DMF containing dissolved SPEEK and clay are sonicated for about 4 minutes using an Ultrasonic Homogenizer. The sonicated solution is stirred and heated to allow the solvent (DMF) to evaporate. Heating and stirring continue until the solution thickens and attains a casting consistency.
  • DMF N,N-dimethyl formaldehyde
  • the polymer and/or composite polymer solution may be prepared by using any of the solvents not limited to N,N-dimethyl formaldehyde, N,N-dimethyl acetamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide alcohols such as isopropyl alcohol, and t-butyl alcohol.
  • the solution is degassed in a vacuum oven. After vacuum treatment, the resulting solution is poured out onto a clean glass plate and cast into approximately 50 ⁇ m thick films using a doctor blade.
  • the curing protocol proceeds as follows: first, the cast film is annealed in a convection oven for about 12 hours at about 70 °C; next, the cast film is placed in a vacuum oven for about 12 hours at about 100°C; after which it is subjected to vacuum for approximately 12 hours in an oven which is maintained at about 130°C. Then, the cured films are peeled off the glass plate using a blade and protonated. The films are stored in ultra-pure water until ready for use. In testing, proton exchange membranes produced by the foregoing method showed improved mechanical properties, water uptake, and conductivity over unmodified SPEEK of the same sulfonation level.

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Abstract

La présente invention a trait à des membranes électrolytiques en polymère économiques contenant des matériaux échangeurs de cations inorganiques comprenant diverses charges variées à base d'argile fabriquées par la coulée en solution. Les membranes présentent une capacité supérieure d'échange d'ions, de conductivité protonique et/ou de croisement de gaz inférieur. De manière générale, les membranes composites présentent d'excellentes propriétés physico-chimiques et une efficacité de pile supérieure dans des piles à combustible hydrogène-oxygène.
PCT/US2004/001960 2002-12-05 2004-01-23 Electrolytes en polymere composite pour piles a combustibles a membrane echangeuse de protons WO2005020362A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
EP04704918A EP1665438A1 (fr) 2003-08-19 2004-01-23 Electrolytes en polymere composite pour piles a combustibles a membrane echangeuse de protons
JP2006523816A JP2007503089A (ja) 2003-08-19 2004-01-23 プロトン交換膜燃料電池用の複合高分子電解質

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PCT/US2002/039104 WO2004015801A1 (fr) 2002-08-13 2002-12-05 Electrolyte composite pour piles a combustible
US10/644,227 2003-08-19

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Cited By (6)

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WO2010031877A1 (fr) * 2008-09-22 2010-03-25 Nanologica Ab Membranes poreuses hybrides au silice-polycarbonate et répliques de polycarbonate poreuses obtenues à partir de ces membranes
CN106000133A (zh) * 2016-06-25 2016-10-12 贵州省材料技术创新基地 聚砜-热塑性弹性体-有机蒙脱土共混中空纤维膜及其制备方法
IT201700115604A1 (it) * 2017-10-14 2019-04-14 Spin Pet Srl Processo per una membrana anionica nanostrutturata innovativa basata su un copolimero a catena laterale epossidica ed argilla stratificata modificata per elettrolisi e celle a combustibile.
CN114288855A (zh) * 2021-11-25 2022-04-08 国家电投集团氢能科技发展有限公司 一种水电解膜及其制备方法
CN115295845A (zh) * 2022-08-25 2022-11-04 湖北工业大学 一种氢燃料电池用质子交换膜及其制备方法和应用
CN118320642A (zh) * 2024-04-17 2024-07-12 水伏能源科技(上海)有限公司 一种蛭石纳米片复合薄膜及其制备方法

Citations (3)

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US6509441B1 (en) * 1998-03-27 2003-01-21 Universitat Stuttgart Modified polymer and modified polymer membranes
US6562891B1 (en) * 1999-12-17 2003-05-13 Industrial Technology Research Institute Modified clay minerals and polymer composites comprising the same
US6602630B1 (en) * 2000-03-14 2003-08-05 The Electrosynthesis Company, Inc. Membrane electrode assemblies for electrochemical cells

Patent Citations (3)

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Publication number Priority date Publication date Assignee Title
US6509441B1 (en) * 1998-03-27 2003-01-21 Universitat Stuttgart Modified polymer and modified polymer membranes
US6562891B1 (en) * 1999-12-17 2003-05-13 Industrial Technology Research Institute Modified clay minerals and polymer composites comprising the same
US6602630B1 (en) * 2000-03-14 2003-08-05 The Electrosynthesis Company, Inc. Membrane electrode assemblies for electrochemical cells

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010031877A1 (fr) * 2008-09-22 2010-03-25 Nanologica Ab Membranes poreuses hybrides au silice-polycarbonate et répliques de polycarbonate poreuses obtenues à partir de ces membranes
CN106000133A (zh) * 2016-06-25 2016-10-12 贵州省材料技术创新基地 聚砜-热塑性弹性体-有机蒙脱土共混中空纤维膜及其制备方法
IT201700115604A1 (it) * 2017-10-14 2019-04-14 Spin Pet Srl Processo per una membrana anionica nanostrutturata innovativa basata su un copolimero a catena laterale epossidica ed argilla stratificata modificata per elettrolisi e celle a combustibile.
CN114288855A (zh) * 2021-11-25 2022-04-08 国家电投集团氢能科技发展有限公司 一种水电解膜及其制备方法
CN114288855B (zh) * 2021-11-25 2023-03-10 国家电投集团氢能科技发展有限公司 一种水电解膜及其制备方法
CN115295845A (zh) * 2022-08-25 2022-11-04 湖北工业大学 一种氢燃料电池用质子交换膜及其制备方法和应用
CN118320642A (zh) * 2024-04-17 2024-07-12 水伏能源科技(上海)有限公司 一种蛭石纳米片复合薄膜及其制备方法

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