BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be more fully understood by reference to the following drawings which are for illustrative purposes only:
FIGS. 1A and 1B show the roll bonder for carrying out the present invention according to the GDE/membrane process.
FIGS. 2A and 2B show before and after views of bonding of the present invention according to the GDE/membrane process.
FIGS. 3A and 3B show the before and after bonding of the present invention according to the 2-layer MEA/GDL process.
FIGS. 4A and 4B schematically show the roll bonder for carrying out the present invention according to the 2-layer MEA/GDL process.
FIGS. 5A-5D are views of the bonding of the MEA of the present invention according to the precursor-MEA/GDE process.
FIGS. 6A-6D are views of the before and after bonding of the MEA of the present invention according to the double precursor-MEA process.
FIGS. 7A and 7B show the use of the MEA of the present invention with a bipolar separator plate.
DETAILED DESCRIPTION OF THE INVENTION
Referring more specifically to the drawings, for illustrative purposes the present invention is embodied in the apparatus and method generally shown in FIG. 1A through FIG. 7B. It will be appreciated that the apparatus may vary as to configuration and as to details of the parts, and that the method may vary as to the specific steps and sequence, without departing from the basic concepts as disclosed herein.
Membrane electrode assemblies (MEAs) are produced in accordance with this invention by combining gas diffusion layers, catalyst/electrodes and a polymer electrolyte membrane in a continuous rolling and bonding process. These components can be combined in various sequences to achieve the end goal of producing a more economical MEA by mechanically stabilizing the flimsy electrolyte membrane material.
A precursor-MEA is produced in accordance with this invention by attaching or bonding a polymer electrolyte membrane to a gas diffusion layer by one of two preferred embodiments. FIGS. 1A and 1B show a first embodiment, gas diffusion electrode material (GDE) 18 such as that supplied by the E-TEK Division of PEMEAS Fuel Cell Technologies on a roll 10 is mated or bonded with a polymer electrolyte membrane material 17 such NAFION® by DuPont, also supplied on a roll 11, forming a unified structure. The GDE material can preferably be a cathode but can alternately be an anode. The two materials are unwound and roll bonded or laminated with the use of heat 12 at a temperature of about 50 C to 200 C and pressure 13, 14 of about 50 psi to 300 psi in such a manner that the catalyst/electrode side of the GDE is in contact with the polymer electrolyte membrane material. The temperature and pressure make the ionomer in the catalyst layer soft and adhesive to provide a good bond between the gas diffusion layer and the catalyst/electrode and between the catalyst/electrode and the polymer electrolyte membrane forming a unified structure. After bonding the precursor-MEA is either rolled for storage 15 or sized by die cutting, shearing or other sizing methods 16 known to those familiar with the art. FIG. 2A shows the GDE 25 and the electrolyte membrane material before bonding. The GDE 18 consists of the catalyst/electrode 21 and the GDL 22 as a unit. The bonded, sized precursor-MEA 26 is shown in cross section in FIG. 2B showing the polymer electrolyte membrane material 17, the catalyst/electrode 21 and the gas diffusion layer 22 as a unified structure. This 3-layer precursor-MEA consists of polymer electrolyte membrane material 17, the catalyst/electrode 21 and the gas diffusion layer 22 as a unified structure. Note that the edges of the polymer electrolyte membrane material 17, the catalyst/electrode 21 and the gas diffusion layer 22 are sized to be flush on the edges 23, 24 as are the other edges of the unified structure which are not shown. As a unified structure, the precursor-MEA has the advantage eliminating the separate handling of the polymer electrolyte membrane material itself because it is bonded to the GDL material in a unified structure, which is easier to manipulate. A variation of this embodiment, rather than continuous roll bonding of the material, is to use individual sections of the materials and hot-press or hot roll the sections of the GDE and the polymer electrolyte membrane material using similar temperatures and pressures to form the unified structure. An additional variation is the formation of the polymer electrolyte membrane in situ by coating the GDE with a NAFION ionomer solution, which is cured as described in the teachings of U.S. Pat. No. 6,641,862, to form the unified structure.
A second embodiment of the method of producing the precursor-MEA, shown in FIGS. 3A-3B, is to use a polymer electrolyte membrane 17 onto which a catalyst/electrode 21 has been applied/bonded to one side of the polymer electrolyte membrane material, forming a 2-layer MEA 35 having the electrolyte membrane material 17 with the catalyst/electrode 21 essentially covering the entire one side of the electrolyte membrane material 17, with no need for borders or frames as is the usual practice. The 2-layer MEA 35 can preferably be a cathode but can alternately be an anode. U.S. Pat. Nos. 6,197,147; 6,933,033; and 6,855,178 teach methods of applying a catalyst/electrode to a polymer electrolyte membrane. Polymer electrolyte material with catalyst/electrodes bonded on is supplied by DuPont, W. L. Gore, and Ion Power, among others. Gas diffusion layer material (GDL) 22 such as that supplied by the E-TEK Division of PEMEAS Fuel Cell Technologies, Toray Industries, Inc. and SGL Carbon AG on a roll 40 is mated or bonded with the 2-layer MEA material 35, also supplied on a roll 41, to form a unified structure (FIGS. 4A-4B). The two materials are unwound and roll bonded or laminated with the use of heat 12 at a temperature of about 50 C to 200 C and pressure 13, 14 of about 50 psi to 300 psi in such a manner that the catalyst/electrode side of the 2-layer MEA is in contact with the gas diffusion layer material 22. The temperature and pressure make the ionomer in the catalyst layer soft and adhesive to provide a good bond between the gas diffusion layer and the catalyst/electrode and between the catalyst/electrode and the polymer electrolyte membrane forming the unified structure. After bonding, the precursor-MEA is either rolled for storage 15 or sized by die cutting, shearing or other sizing methods 16 known to those familiar with the art. FIG. 3A shows the GDL 22 and the 2-layer MEA 35 before bonding. The 2-layer MEA consists of the catalyst/electrode 21 and the polymer electrolyte membrane 17 as a unit. The sized precursor-MEA 26 is shown in cross section in FIG. 3B, showing the polymer electrolyte membrane material 17, the catalyst/electrode 21 and the gas diffusion layer 22. This 3-layer precursor-MEA 26 consists of polymer electrolyte membrane material 17, the catalyst/electrode 21, and the gas diffusion layer 22 as a unified structure. Note that the edges of the polymer electrolyte membrane material 17, the catalyst/electrode 21 and the gas diffusion layer 22 are sized to be flush on the edges 23, 24 as are the remaining edges for the unified structure not shown. This precursor-MEA 26 has the advantage of eliminating the handling of the polymer electrolyte membrane material itself, because it is bonded to the GDL material, which is easier to manipulate as a unified structure. A variation of this embodiment is to use individual sections of the materials and hot-press the sections of the GDE and the polymer electrolyte membrane material using similar temperatures and pressures, rather than use continuous roll bonding of the material.
A precursor-MEA is produced in accordance with the second embodiment, shown in FIGS. 4A and 4B, by attaching or bonding a 2-layer MEA 35 to gas diffusion layer 22 in a roll bonding processes. The 2-layer MEA material 35 is supplied on a roll 41 and is mated or bonded with a GDL material 22, also supplied as a roll 40, forming a unified structure. The two materials are unwound and roll bonded or laminated with the use of heat 12 at a temperature of about 50 C to 200 C and pressure 13, 14 of about 50 psi to 300 psi in such a manner that the catalyst/electrode 21 side of the 2-layer MEA 35 is in contact with the GDL material 22. The temperature and pressure make the ionomer in the catalyst layer soft and adhesive to provide a good bond between the gas diffusion layer and the catalyst/electrode and between the catalyst/electrode and the polymer electrolyte membrane forming a unified structure. After bonding, the precursor-MEA is either rolled for storage 15 or sized by die cutting, shearing or other sizing methods 16 known to those familiar with the art.
FIGS. 5A-5D are exemplary illustrations for fabricating MEAs from precursor-MEAs 26. FIG. 5A illustrates the sized precursor-MEA 26 from the embodiments described hereinabove showing the polymer electrolyte membrane 17 on the obverse and a sized GDE 51 showing the GDL on the obverse 22, which is sized to be smaller in the planar dimensions than the precursor-MEA 26. If the precursor-MEA 26 is the cathode, the GDE 51 is an anode; conversely, if the precursor-MEA is an anode, then the GDE 51 is a cathode. The precursor-MEA 26 and the GDE 51 are brought into registration (FIG. 5B) by means of transport, feeding and registering devices known to those familiar with the art. The placement of the sized precursor-MEA 26 is such that there is a border area 52 continuously around and outboard of the sized GDE 51. This border area is the exposed supported polymer electrolyte membrane 17 of the precursor-MEA 26. FIG. 5C shows the cross sectional configuration of the sized precursor-MEA 26 and the second sized GDE 51 before bonding. The polymer electrolyte membrane 17 of the precursor-MEA 26 is caused to contact the catalyst/electrode 21 of the sized GDE 51. The two components, the polymer electrolyte membrane 17 of the precursor-MEA 26 and the catalyst/electrode 21 (not shown) of the sized GDE 51 are laminated and bonded by hot-pressing or roll bonding with the use of heat at a temperature of about 50 C to 200 C and pressure of about 50 psi to 300 psi in such a manner that the catalyst/electrode side 21 of the GDE is in contact with the polymer electrolyte membrane 17 of the precursor-MEA 26. The temperature and pressure make the ionomer in the catalyst layer soft and adhesive to provide a good bond between the gas diffusion layer of sized GDE 51 and the and the polymer electrolyte membrane 17 layer of the precursor-MEA 26. FIG. 5D shows a cross section of the bonded or laminated MEA 50 showing the border area 52 which extends outboard from the bonded GDE 51. In a variation of this embodiment, the border area 52 is eliminated and the edges 54, 55 of the sized GDE 51 extend to be coincident with the edges 23, 24, shown, of the precursor-MEA 26. The remaining edges of the sized GDE 51, not shown, extend to be coincident with the corresponding edges, not shown, of the precursor-MEA 26.
An alternate embodiment for fabricating MEAs from precursor-MEAs 26 is shown in the exemplary illustrations of FIGS. 6A-D. FIG. 6A illustrates a first sized precursor-MEA 26 from the embodiments described hereinabove showing the polymer electrolyte membrane 17 on the obverse and a second sized precursor-MEA 60 showing the GDL on the obverse 22 which is sized to be smaller in both planer dimensions than the first precursor-MEA 26. If the first precursor-MEA 26 is the cathode, then the second sized precursor-MEA 60 is an anode; conversely, if the precursor-MEA is an anode, then the second sized precursor-MEA 60 is a cathode. The first precursor-MEA 26 and the second precursor-MEA 60 are brought into registration, FIG. 6B, by means of transport, feeding and registering devices known to those familiar with the art. The placement of the second precursor-MEA 60 is such that there is a border area 61 continuously around and outboard of the second precursor-MEA 60. This border area is the exposed supported polymer electrolyte membrane 17 of the first precursor-MEA 26. FIG. 6C shows the cross sectional configuration of the first sized precursor-MEA 26 and the second sized precursor-MEA 60 before bonding. The polymer electrolyte membrane 17 of the first precursor-MEA 26 is caused to contact the polymer electrolyte membrane 62 of the second precursor-MEA 60. The two components, the polymer electrolyte membrane 17 of the first precursor-MEA 26 and the polymer electrolyte membrane 62 of the second precursor-MEA 60 of the second precursor-MEA 60, are laminated and bonded by hot-pressing or roll bonding with the use of heat at a temperature of about 50 C to 200 C and pressure of about 50 psi to 300 psi in such a manner that the electrolyte membrane 17 of the first precursor-MEA 26 is in contact with the polymer electrolyte membrane 62 of the second precursor-MEA 60. The temperature and pressure make the polymer electrolyte membrane 17 of the first precursor-MEA 26 and the polymer electrolyte membrane 62 of the second precursor-MEA 60 soft and adhesive to provide a good bond between the polymer electrolyte membrane 17 of the first precursor-MEA 26 and the polymer electrolyte membrane 62 of the second precursor-MEA 60. FIG. 6D shows a cross section of the bonded or laminated MEA 50 showing the border area 61 which extends outboard from the bonded second precursor-MEA 60. In a variation of this embodiment, the border area 61 is eliminated and the edges, 67, 68 of the second sized precursor-MEA 60 extend to be coincident with the edges 23, 24, shown, of the first precursor-MEA 26. The remaining edges of the second precursor-MEA, not shown, extend to be coincident with the corresponding edges, not shown, of the first precursor-MEA 26.
Referring to FIGS. 7A and 7B, the border areas 52, 61 are used as sealing or bonding surfaces to seal or bond the MEAs 50, 66 to an adjacent bipolar separator plate 72, 76 in an arrangement known to those proficient in the art. The seals or bonds 71, 75 are gaskets, gaskets incorporating adhesives, o-rings, pressure sensitive adhesives with or without a carrier gasket, liquid or semi-liquid adhesives. Any adhesives or gaskets incorporating adhesives necessarily must form an adequate bond with the bipolar separator plates 72, 76 and the membrane electrode assemblies' 50, 66 border areas 52, 61 and between the bipolar separator plates 72, 76 and the membrane electrode assembly 50, 66. Below are a few examples of adhesives, which may be of use in bonding the MEAs and manifolds to the BSPs:
Specific commercial tapes of the 3M Corp. (of St. Paul, Minn.) family of VHB (Very High Bond) Tapes, such as product number 4920, a closed-cell acrylic foam carrier with adhesive, or F-9469 PC, an adhesive transfer tape (trademarks of the 3M Company of St. Paul Minn.).
Commercial acrylic adhesives such as Loctite Product 312 or 326 (trademark of the Loctite Corporation of Rocky Hill, Conn.) or 3M Scotch-Weld Acrylic Adhesive such as DP-805 or DP-820 (trademark of the 3M Company St. Paul Minn.).
Specific epoxy products such as 3M 1838 (trademark of the 3M Company of St. Paul Minn.) or Loctite E-20HP. (Trademark of the Loctite Corporation of Rocky Hill, Conn.)
These examples are not to imply the only materials applicable to the bonding of the MEAs and the BSPs, but only illustrate some of the suitable materials that can be selected by those skilled in the art. These materials are applied with the typical methods made use of by those skilled in the art such as hand or robotic placement, hand or robotic dispensing, screen or stencil printing, rolling and spraying.
While only a few embodiments of the invention have been shown and described herein, it will become apparent upon reading this application to those skilled in the art that various modifications and changes can be made to provide MEAs for fuel cells in a fully functioning fuel cell device without departing from the spirit and scope of the present invention. The present approach to produce a novel fuel cell MEA is applicable to generally any cell geometry or configuration, such as rectangular, square, round or any other planar geometry or configuration. All such modifications and changes coming within the scope of the appended claims are intended to be carried out thereby.
Although the description above contains many details, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments of this invention. Therefore, it will be appreciated that the scope of the present invention fully encompasses other embodiments which may become obvious to those skilled in the art, and that the scope of the present invention is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.” All structural, chemical, and functional equivalents to the elements of the above-described preferred embodiment that are known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the present claims. Moreover, it is not necessary for a device or method to address each and every problem sought to be solved by the present invention, for it to be encompassed by the present claims. Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. No claim element herein is to be construed under the provisions of 35 U.S.C. 112, sixth paragraph, unless the element is expressly recited using the phrase “means for.”
Patent Application
20080057380
