DE102013205284A1 - Making a membrane electrode assembly comprises applying a porous reinforcement layer to the wet ionomer layer - Google Patents

Making a membrane electrode assembly comprises applying a porous reinforcement layer to the wet ionomer layer

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Publication number
DE102013205284A1
DE102013205284A1 DE201310205284 DE102013205284A DE102013205284A1 DE 102013205284 A1 DE102013205284 A1 DE 102013205284A1 DE 201310205284 DE201310205284 DE 201310205284 DE 102013205284 A DE102013205284 A DE 102013205284A DE 102013205284 A1 DE102013205284 A1 DE 102013205284A1
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Prior art keywords
layer
ionomer
wet
catalyst
electrode assembly
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DE201310205284
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German (de)
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Scott C. Moose
Scott L. Peters
Timothy J. Fuller
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GM Global Technology Operations LLC
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GM Global Technology Operations LLC
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Priority to US13/434,898 priority Critical patent/US9780399B2/en
Priority to US13/434,898 priority
Application filed by GM Global Technology Operations LLC filed Critical GM Global Technology Operations LLC
Publication of DE102013205284A1 publication Critical patent/DE102013205284A1/en
Pending legal-status Critical Current

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    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00Fuel cells; Manufacture thereof
    • H01M8/10Fuel cells with solid electrolytes
    • H01M8/1004Fuel cells with solid electrolytes characterised by membrane-electrode assemblies [MEA]
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00Fuel cells; Manufacture thereof
    • H01M8/10Fuel cells with solid electrolytes
    • H01M8/1016Fuel cells with solid electrolytes characterised by the electrolyte material
    • H01M8/1018Polymeric electrolyte materials
    • H01M8/1041Polymer electrolyte composites, mixtures or blends
    • H01M8/1053Polymer electrolyte composites, mixtures or blends consisting of layers of polymers with at least one layer being ionically conductive
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00Fuel cells; Manufacture thereof
    • H01M8/10Fuel cells with solid electrolytes
    • H01M8/1016Fuel cells with solid electrolytes characterised by the electrolyte material
    • H01M8/1018Polymeric electrolyte materials
    • H01M8/1069Polymeric electrolyte materials characterised by the manufacturing processes
    • H01M8/1081Polymeric electrolyte materials characterised by the manufacturing processes starting from solutions, dispersions or slurries exclusively of polymers
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00Fuel cells; Manufacture thereof
    • H01M8/10Fuel cells with solid electrolytes
    • H01M2008/1095Fuel cells with polymeric electrolytes
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00Fuel cells; Manufacture thereof
    • H01M8/10Fuel cells with solid electrolytes
    • H01M8/1016Fuel cells with solid electrolytes characterised by the electrolyte material
    • H01M8/1018Polymeric electrolyte materials
    • H01M8/102Polymeric electrolyte materials characterised by the chemical structure of the main chain of the ion-conducting polymer
    • H01M8/1023Polymeric electrolyte materials characterised by the chemical structure of the main chain of the ion-conducting polymer having only carbon, e.g. polyarylenes, polystyrenes or polybutadiene-styrenes
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00Fuel cells; Manufacture thereof
    • H01M8/10Fuel cells with solid electrolytes
    • H01M8/1016Fuel cells with solid electrolytes characterised by the electrolyte material
    • H01M8/1018Polymeric electrolyte materials
    • H01M8/1039Polymeric electrolyte materials halogenated, e.g. sulfonated polyvinylidene fluorides
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02PCLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50Manufacturing or production processes characterised by the final manufactured product
    • Y02P70/56Manufacturing of fuel cells

Abstract

Making a membrane electrode assembly comprises forming a reinforced polymer electrolyte membrane on the first catalyst coated diffusion media, the forming comprising: coating a first ionomer solution onto the first catalyst coated diffusion media to form a first wet ionomer layer on its surface; and applying a porous reinforcement layer to the first wet ionomer layer such that the first wet ionomer layer at least partially impregnates the reinforcement layer. Making a membrane electrode assembly comprises providing a first catalyst coated diffusion media; and forming a reinforced polymer electrolyte membrane on the first catalyst coated diffusion media, the forming comprising: coating a first ionomer solution onto the first catalyst coated diffusion media to form a first wet ionomer layer on its surface; applying a porous reinforcement layer to the first wet ionomer layer such that the first wet ionomer layer at least partially impregnates the reinforcement layer; and drying the first wet ionomer layer with the impregnated reinforcement layer. An independent claim is a membrane electrode assembly comprising: at least one catalyst coated gas diffusion media; and a reinforced proton exchange membrane layer joined to the catalyst coated gas diffusion media, the reinforced pro-ton exchange membrane layer comprising a first ionomer layer with an integrated porous reinforcement layer.

Description

  • Explanation of related cases
  • This application is partially set forth in U.S. Patent Application Serial No. 11 / 972,817, filed January 11, 2008, entitled "Method of Making a Proton Exchange Membrane Using a Gas Diffusion Electrode as a Substrate," incorporated herein by reference Reference is incorporated.
  • BACKGROUND OF THE INVENTION
  • The present invention relates generally to fuel cells, and more particularly to enhancing polymer membranes used in fuel cells and to methods of producing reinforced polymer membranes such that the structural properties of such membranes are improved.
  • Fuel cells, also referred to as electrochemical conversion cells, generate electrical energy by processing reactants, for example by the oxidation and reduction of hydrogen and oxygen. Hydrogen is a very attractive fuel because it is pure and can be used to efficiently generate electricity in a fuel cell. The automotive industry is spending significant resources in the development of hydrogen fuel cells as an energy source for vehicles. Hydrogen fuel cell powered vehicles would be more efficient and produce fewer emissions than current vehicles using internal combustion engines.
  • In a typical fuel cell system, hydrogen or a hydrogen-rich gas is supplied as a reactant via a flow path to the anode side of a fuel cell while oxygen (such as in the form of atmospheric oxygen) is supplied as a reactant via a separate flow path to the cathode side of the fuel cell becomes. Catalysts, typically in the form of a noble metal such as. Platinum are disposed at the anode and cathode to facilitate the electrochemical conversion of the reactants to electrons and positively charged ions (for the hydrogen) and negatively charged ions (for the oxygen). In a well known fuel cell form, the anode and cathode may be made of a layer of electrically conductive gas diffusion media (GDM) material on which the catalysts are deposited to form a catalyst coated diffusion media (CCDM) , An electrolyte layer (also known as a proton transmissive or proton conductive ionomer layer) separates the anode from the cathode to allow the selective passage of positively charged ions to pass from the anode to the cathode while preventing the passage of the generated electrons instead, they are forced to flow through an external electrically conductive circuit (eg, a load) to do useful work before recombining with the charged ions at the cathode. The combination of the positively and negatively charged ions at the cathode results in the production of environmentally friendly water as a by-product of the reaction. In another well-known fuel cell mold, the anode and the cathode may be formed directly on the electrolyte layer to form a structure known as a cathode coated membrane (CCM). Regardless of whether the configuration is CCDM based or CCM based, the resulting combination of one or more electrodes mounted on one or both opposite sides of the proton conductive medium is known as a membrane electrode assembly (MEA).
  • A fuel cell design, referred to as the proton exchange membrane or polymer electrolyte membrane (in each case, PEM, or polymer electrolyte membrane) fuel cell, has been found to be particularly promising for vehicle and similar mobile applications. The proton conductive membrane, which forms the electrolyte layer of a PEM fuel cell, is in the form of a solid ((z. B. a perfluorosulfonic PFSA, from the English. Perfluorosulfonic acid) -Ionomerschicht is for a commercially available example, Nafion ®) available , An MEA such. The above-mentioned, when configured to receive reactants via a corresponding flow path (such as a bipolar plate or other fluid supply device) forms a single PEM fuel cell; many such single cells may be combined to form a fuel cell stack to increase the power output thereof. Multiple batches can be coupled together to further increase power output.
  • Despite the advances, one of the problems with current PEM fuel cell technology is that forming an MEA from a free-standing electrolyte layer is costly.
  • SUMMARY OF THE INVENTION
  • In accordance with one aspect of the teachings of the present invention, a method of making an MEA is disclosed which comprises providing a first CCDM, coating a first ionomer solution on the CCDM to form a first wet ionomer layer, a porous reinforcement layer the wet ionomer layer is applied such that the wet ionomer layer impregnates at least a portion of the reinforcing layer and the wet ionomer layer with the impregnated reinforcing layer is dried to form a PEM layer. The concept of an MEA, while traditionally understood to embrace both electrodes (ie, an anode and a cathode) attached to the membrane, is expanded in the present invention to include the subunit which has an arrangement of only one of the subunits Electrodes and the membrane comprises; the nature of the pending variant will be apparent from the context.
  • Optionally, a second ionomer solution may be deposited on or otherwise formed on a second CCDM to form a second wet ionomer layer; As with the first wet ionomer layer discussed above, the second wet ionomer layer may be dried, either substantially simultaneously or sequentially with respect to the first wet ionomer layer. Likewise, after drying by hot pressing, laminating, or a similar procedure, the second ionomer layer may be joined to one or both of the reinforced PEM layer and the second CCDM. Alternatively, a second ionomer solution may be deposited on the first wet ionomer layer that has been impregnated with the reinforcing layer. An electrode may be attached to and attached to the first or second dried ionomer layer. The ionomers in the first and second solutions may be the same or different and either or both may include a solvent. Likewise, the ionomers may be based on sulfonated polyether ketones, aryl ketones, polybenzimidazoles, PFSAs, perfluorocyclobutanes (PFCBs) or the like, while the ionomer solutions may further comprise chemical degradation agents to reduce the likelihood of chemical damage to the proton exchange membrane layer. As mentioned above, the porous reinforcing layer may be made of a polymer film, a woven fabric or combinations thereof.
  • According to another aspect of the invention, an integrally reinforced MEA is disclosed. In one embodiment, the electrode assembly includes a CCDM and a reinforced PEM layer on the CCDM, wherein the enhanced relationship between the PEM layer and the CCDM results from an integrated coupling of the otherwise structurally non-self-supporting ionomer and a porous reinforcing layer.
  • The integrated porous reinforcement layer is optionally made of a polymeric film, a woven fabric or a combination thereof, as discussed above in connection with the previous aspect. The MEA may further comprise a second ionomer layer formed on a surface of the reinforced PEM layer so that the second ionomer layer is disposed on the side of the reinforcing material opposite to the first ionomer layer. The ionomer in the second ionomer layer may be different or the same from the ionomer in the first ionomer layer. Similarly, the one or more ionomer layers may be made from the materials mentioned above in connection with the previous aspect including PFSA, PFCB or similar hydrocarbon ionomers. The MEA may form the basis for a fuel cell, which in turn may be a source of propulsion power for a car, truck, motorcycle, or similar motor vehicle.
  • BRIEF DESCRIPTION OF THE DRAWINGS
  • The following detailed description of the preferred embodiments of the present invention is best understood when read in conjunction with the following drawings in which like structures are designated by like reference numerals and in which:
  • 1A shows a schematic cross section of an embodiment of a fuel cell according to the prior art with a free-standing PEM, which is surrounded on opposite sides of CCDMs;
  • 1B shows a schematic cross section of another embodiment of a fuel cell according to the prior art with a free-standing PEM in the form of an MEA;
  • 2 Figure 3 is a cross section of one embodiment of a CCM;
  • 3 Figure 3 is a cross section of one embodiment of a CCDM;
  • 4 Figure 3 is an illustration of a method of making an MEA using an electrode assembly with an integrated reinforcement layer;
  • 5 Figure 4 is an illustration of another method of making an MEA using an electrode assembly with an integrated reinforcement layer;
  • 6 Fig. 12 is an illustration of a polarization chart for a cathode CCDM manufactured according to a first example;
  • 7 Fig. 11 is an illustration of a polarization chart for a cathode CCDM manufactured according to a second example; and
  • 8th FIG. 4 is an illustration of yet another method of making an MEA using an electrode assembly having an integrated reinforcement layer. FIG.
  • DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
  • The invention relates to integrally reinforced MEAs for fuel cells. A reinforcing layer is integrated into a wet ionomer layer coated on a CCDM electrode. The reinforcing material will make the entire electrode assembly more durable and less susceptible to short circuit defects. In addition, the use of the reinforcing layer may also allow the entire proton exchange membrane layer to be thinner than a free standing PEM (also referred to herein as stand-alone). By this construction, the reinforcement of the coated ionomer layer serves to mimic the structural and electrochemical properties of a conventional free-standing PEM with a much smaller mass or weight. Furthermore, the approach of the present invention would further reduce the amount of ionomer used and, as a result, the cost of the structure.
  • At the beginning referring to the 1A and 1B show partial sectional views of a PEM fuel cell 10 in Explosionsdarstellungsform an embodiment on CCDM basis or a design based on CCM. In any case, the fuel cell includes 10 a substantially flat, stand-alone PEM 15 and a pair of catalyst layers 20 (which individually as Anodenkatalysatorschicht 20A and as a cathode catalyst layer 20B which are adjacent corresponding opposite sides of the PEM 15 are facing). It is also a pair of diffusion layers 30 (individually as an anode diffusion layer 30A and as a cathode diffusion layer 30B which are in facing contact with the anode catalyst layer 20A or the cathode catalyst layer are arranged). As shown in the figures, the cathode diffusion layer 30B thicker than the anode diffusion layer 30A , However, those skilled in the art will appreciate that such differences in thickness for the operation of the fuel cell 10 are not necessary and instead may have a substantially same thickness. It will be equally apparent to those skilled in the art that the anode diffusion layer 30A and the cathode diffusion layer 30B may be made of the same or different materials, and that each variant is within the scope of the present invention. bipolar plates 40 are provided with many channels to allow reactant gases to be the corresponding side of the catalyst layers 20A and 20B as well as the PEM 15 to reach. The diffusion layers 30 can make electrical contact between the respective catalyst layers 20 and the bipolar plates 40 provide, which can additionally serve as current collectors. Each of the diffusion layers 30 may be made to define a generally porous structure to prevent the passage of gaseous reactants to the catalyst layers 20 to facilitate. Suitable materials for the diffusion layers 30 may include, but are not limited to, carbon paper, porous graphite, felts, cloth, cloth, or woven or nonwoven materials that include some degree of porosity.
  • In the CCDM-based approach of 1A serves any diffusion layer 30 as the aforementioned GDM or gas diffusion layer (GDL) serving as a substrate for the catalyst layers 20 can be used, which can be deposited (for example) in ink form. In the CCM-based approach of 1B define the stand-alone PEM 15 and the catalyst layers 20A . 20B collectively, the MEA 50 , In each of the CCDM-based embodiment and the CCM-based embodiment, the catalyst layers 20 attached to, deposited on, embedded in or otherwise joined to the respective diffusion layers. As professionals will see, bringing a freestanding PEM 15 additional manufacturing steps with it, regardless of whether the resulting MEA 50 a CCDM-based embodiment, in the anode and cathode layers 20A . 20B at respective diffusion layers 30A . 30B are attached or these same layers 20A . 20B as part of a CCM-based design at PEM 15 are attached.
  • Referring next to 2 is a single CCDM 100 which can be used as a carrier for an ionomer layer (explained in more detail below). As explained above, a CCDM is made by placing a catalyst layer 103 (also known as an electrode layer) is mounted on or otherwise bonded to a GDM, which is a diffusion media substrate 101 with a microporous layer 102 comprising, wherein the microporous layer 102 with a gas diffusion to and a water removal from the electrode layer 103 helps. As explained below and shown in the accompanying drawings, the CCDM 100 be individually marked (eg with 100A . 100B or the like) to take account of embodiments in which multiple (and possibly different) CCDMs are used. The catalyst layer 103 may suitable catalytic particles, for. For example, metals such as Include platinum, platinum alloys, and other catalysts known to those skilled in the art of fuel cells, and may be prepared by any suitable method such as. z. As rolling, painting, spraying, a Meyer rod, a slot die, a comma bar or the like can be applied. The diffusion medium substrate 101 may be a conventional fuel cell gas diffusion media material, e.g. As a non-woven carbon fiber paper, a fiber fabric or a carbon foam. Likewise, the microporous layer 102 which may comprise particles and a binder, by any suitable method such as. As the aforementioned be applied. Suitable particles may include, but are not limited to, graphitic, graphitized, or other conductive carbon particles, while suitable microporous layer binders 102 at least one of PTFE, polyvinylidene fluoride (PVDF), fluorinated ethylene propylene (FEP), or other organic or inorganic hydrophobic materials.
  • Referring next to the 3 to 5 are various methods of making an integrally reinforced MEA 170 shown by the approach of the present invention. With special reference to 3 becomes an ionomer solution 110A on a first CCDM 100A coated to a PEM precursor layer 115 to build. The ionomer solution 110 typically includes one or more solvents and may include additional materials such as compounds to improve the performance and durability of the resulting membrane. That in the solution 110A used ionomer can be prepared from any commercially available variant such. B the aforementioned PFSA, PFCB or hydrocarbon ionomers such. As sulfonated polyether ketones, aryl ketones and polybenzimidazoles exist. Other proton-conducting polymers could also be used.
  • The ionomer solution 110A can be applied to the first CCDM by any suitable method, including, but not limited to, casting, laminating, soaking, spraying, a slot die, extrusion, bar coating or other conventional liquid coating methods 100A be deposited. While by the combination of the ionomer solution 110A and the first CCDM 100A formed PEM precursor layer 115 is still wet, a layer of reinforcing material 120 applied. In one form, the reinforcing material 120 be present in the form of a grid or a similar mesh, while in another of a porous material such. PTFE or foamed PTFE (ePTFE). In this latter embodiment, the wet PEM precursor layer is impregnated 115 quickly the pores of the reinforcing material 120 in a manner analogous to when a tissue is used to soak up a spilled liquid when placed over it. The entirety of this integration allows for a first electrode and ionomer assembly 130 the respective sections of a separately formed MEA 50 (such as in the 1A and 1B shown), which on a free-standing proton-conductive membrane 15 based on the state of the art, but without the mass and cost. Thereafter, the first electrode and ionomer assembly 130 a drying 150 subjected.
  • As below left in 3 A second CCDM with a second ionomer layer is shown 110B coated to form a second electrode and ionomer assembly 140 to form which of the first electrode and ionomer assembly 130 except for the presence of the reinforcing material 120 may be similar. As with the first electrode and ionomer assembly 130 may be the second electrode and ionomer assembly 140 a drying step 150 be subjected to solvent removal and curing, curing or otherwise prepare for the next processing step. In a preferred approach, the drying 150 of the two different arrangements 130 and 140 be carried out separately from each other; this would be particularly useful when using different precursor materials, although it will be appreciated by those skilled in the art that the first and second ionomer solutions 110A and 110B can use the same or different materials. The second electrode and ionomer assembly 140 can be determined by any suitable method, such as As hot pressing or laminating 160 with the reinforced first electrode and ionomer assembly 130 combined to the MEA 170 to build. As mentioned above, the first and second electrode and ionomer assemblies are 130 . 140 Subunits of the MEA 170 so that any or all qualify as an assembled membrane and electrode. The first and the second CCDM 100A and 100B may have the same or different structures. In an example of a difference, as mentioned above, the second CCDM 100B (if configured to the cathode side of the MEA 170 occupy) in either the composition material or the dimension to be thicker than the first CCDM 100A on the anode side of the MEA 170 is used. It is important in the present context to point out that each of the 3 to 5 assume that a second ionomer layer 100B either on top of the first electrode and ionomer assembly 130 (as in the 4 and 5 shown) or on the second CCDM 100B (as in 3 shown) is applied. Nevertheless, another valid construction is in 8th shown at a first ionomer solution 110A on the first CCDM 100A is coated, after which the reinforcing layer 120 is applied while the coating is wet to a first electrode and ionomer assembly 130 to produce which in the 3 to 5 is similar. Thereafter, the hot pressing or laminating takes place 160 to the second electrode 100B with an optionally coated thin ionomer layer 105 on the second electrode 100B is coated and then subjected to its own drying step to a modified form 145 of the second electrode and ionomer assembly. After laminating the two electrode ionomer assemblies 130 and 145 each other will be a modified MEA 175 generated, which in the 3 to 5 pictured MEAs 170 with the exception of the second ionomer layer 110B is generally similar. As such, the difference with the embodiment of 8th that the entire first ionomer solution 110A is coated at the beginning, so that the second ionomer solution 110B is not necessary.
  • The reinforcing material 120 may be any porous material that will help provide a backing or reinforcing layer for the resulting MEA 170 provide. Suitable porous materials include, but are not limited to, polymer films, fabrics, and the like, with one particularly useful form of the porous polymer films comprising the aforementioned ePTFE or the like. Because of the convenient recording of the ionomer solution 110A through the layer of reinforcing material 120 The present inventors have found that the application of the reinforcing material 120 as soon as possible on the wet PEM coating 115 the amount of in the CCDM 100A reduced ionomer reduced; this penetration is also due to the porosity and hydrophobicity or hydrophilicity of the CCDM 100A dependent. Penetration also depends on the ionomer liquid formulation (eg, solvent / water ratios, viscosity, solvent type, and ionomer properties such as equivalent weight). Those skilled in the art will also appreciate that, subject to these characteristics, any commercially available CCDM for use as the first and second CCDMs 100A and 100B suitable is.
  • With special reference to 4 may in an alternative approach the second ionomer layer 110B to the first electrode and ionomer assembly 130 in general and on the reinforcing material 120 Section in particular be coated. As more particularly shown, the second ionomer layer becomes 110B on the opposite planar main surface of the reinforcing material 120 from the first ionomer layer 110A coated. In this embodiment, it is preferred that the second ionomer layer 110B directly on the flat surface of the reinforcing material 120 to coat. As with the approach of 3 can this reinforced first electrode and ionomer assembly 130 a drying 150 in general as well as separate sequential drying steps 150 both before and after adding the second ionomer layer 110B be subjected as shown. In one form, the second ionomer layer becomes 110B directly on the surface of the reinforcing material 120 applied after the first ionomer layer 110A is dried while in another form (as in 5 shown) the second ionomer layer 110B can be applied while the first electrode and Ionomeranordnung 130 wet, if desired. In any case, it is preferred that the first and second ionomer layers 110A and 110B dried before the second CCDM 100B is applied. As before, a second CCDM 100B combined to an MEA 170 to produce, this time as a separate layer after drying 150 but before any lamination 160 , Optionally, a thin ionomer layer 105 before lamination 160 on the CCDM 100B coated and dried. Such a layer may be useful in certain hot pressing or similar joining approaches where the surface of the second CCDM 100B serves as a bare electrode without much binding material. By including a thin optional ionomer layer 105 on the bare electrode surface, this is helpful in adhesiveness during subsequent hot pressing or other joining processes.
  • As mentioned above, the ionomer solution 110A (as well as 110B ) Comprise water, alcohols and similar solvents in addition to the proton conductive ionomer. Suitable organic solvents for PFSA include, but are not limited to, alcohols such as e.g. Diacetone alcohol (DAA), isopropyl alcohol (IPA), methanol, ethanol, n-propanol, or combinations thereof. The present inventors have discovered that, depending on the source of ionomer (or the supplier), an alcohol-rich (rather than a water-rich) solution can quickly fill the porous reinforcing material 120 while others require no greater amount of alcohol (or organic solvent) than water. In the present context, an alcohol-rich solvent is one which either contains alcohol as the main ingredient or, in cases where the alcohol does not form the majority, is at least predominantly in terms of weight or volume percent. Other than alcohols, other suitable solvents may include dimethylacetamide, dimethylsulfoxide, N-methyl-2-pyrrolidine, dimethylformamide or combinations thereof. Therefore, when dealing with ionomers where it is desirable that they are rich in alcohol, some water may also be present, although, as mentioned above, optionally in concentrations lower than that of the alcohol or other solvents. On the other hand, in cases where ionomers (such as Nafion® ) less sensitive to these ratios are used, equal amounts (or even high water ratios) may be preferred.
  • The present inventors have also discovered that controlling the viscosity is also a valuable possibility for proper saturation of the reinforcing layer 120 with the ionomer solution 110A sure. One way to change the viscosity, z. For example, adjusting the percentage of solids in the solution; this can be done by dilution or concentration. Alternatively, the ratio of organics to water can control the viscosity. Also, the ionomer is made from known proton conductive materials which include perfluorosulfonic acid, perfluorocyclobutane or hydrocarbon ionomers. Suitable solvents for PFCB include, but are not limited to, dimethylacetamide (DMAC), dimethylsulfoxide (DMSO), N-methyl-2-pyrrolidine (NMP), dimethylformamide (DMF) and alcohols such as e.g. B. the above. The present inventors have found that the reinforcing material 120 surprisingly, with the ionomer solution, with a proper combination of solvents and viscosity 110A easy to fill.
  • As such, the present inventors have found that a number of the above factors affect how quickly and completely the reinforcing material is affected 120 is filled. Therefore, if necessary, the type of ionomer used 110A , the type of alcohol used, the solvent ratio, the viscosity, the time frame of coating the liquid ionomer 110A until the reinforcement material is applied 120 and the nature and properties of the reinforcing material 120 are all considered, although the present inventors believe that the most important factors for a particular ionomer and ionomer supplier are the viscosity, solvent choice and solvent ratio. Generally (as stated above) the ionomer solutions should 110A . 110B to be fast-paced rich in alcohol as opposed to high in water, although it is not absolutely necessary that they are rich in alcohol to the reinforcing material 120 to fill accordingly. Moreover, depending on the nature of the reinforcing material 120 lower alcohols (such as methanol) fail to fill as well as higher alcohols (such as propanols). Therefore, for a hydrophobic reinforcing material such. EPTFE higher alcohols (which also tend to be more hydrophobic) with the reinforcing material 120 to be more compatible (and therefore better able to fill), while ionomer solutions based on lower alcohols used with ePTFE reinforcements do not fill so well. Those skilled in the art will recognize that certain solvents work better with certain ionomers and that tailoring the amount and type of solvent to a particular ionomer is within the scope of the present invention. For example, dilution or otherwise altering the ionomer solution (such as by the addition of n-propyl alcohol) may be used to make filling of the pores faster and more thorough, while other ionomer solutions may not be tolerant to such diluents, and instead require others (such as an ethanol-based solvent). Likewise, the use of water or a higher viscosity may help the deposited ionomer solution at or near the top of the respective porous electrodes of CCDMs 100A and 100B to hold, instead of penetrating them; this is particularly useful in cases where a hydrophobic material (such as PTFE) is present. Since it is expected that the use of one or both of water and a higher viscosity will fill the reinforcing material 120 If desired, the present inventors believe that it may be necessary to create optimal formulation windows for each ionomer material for these two parameters.
  • Referring next to 5 another alternative approach is shown. This will be drying 150 delayed until after the first electrode and ionomer assembly 130 then with a second wet ionomer layer 110B was coated. He is as such the approach of 4 with the exception that only a single drying step 150 is used. This application process ensures that the reinforcing material 120 is completely filled since both of its sides take up the ionomer, the first in the form of the first wet ionomer layer 110A and the second in the form of a second wet ionomer layer 110B , Arranging the second wet ionomer layer 110B immediately after application of the reinforcing material layer 120 can eliminate the need for a separate second coating run, thereby simplifying the process. While it would be possible to eliminate in series the additional coating run by placing two coating stations and the associated drying equipment, such an approach would require additional capital expenditure for this equipment. The in 5 pictured approach with its coating of the second wet ionomer layer 110B on the still wet ionomer assembly 130 eliminates the need for such a double equipment. As with the in 4 In the illustrated embodiment, the embodiment of FIG 5 optionally a thin ionomer layer 105 to facilitate adhesion or bonding.
  • Referring again to 3 became an in-house produced CCDM 100A with an ionomer solution 110A coated, which contained 14.4% by weight of ionomer (in particular, a commercial grade of Nafion ®, which is known as D2020) in 54.3% n-propanol and 45.7% water solvent. In one form, the supplied Nafion ® D2020 ionomer contains about 20-22% solids and a ratio between the volatile organic compound (VOC, from the English. Volatile organic compound) and water of 57.5 / 42.5. Experts will recognize that VOCs are a mixture of different compounds, such as N-propanol, ethanol and some ethers (more than 95% of the VOCs being in the form of n-propanol in a particular form). The present inventors have found that this can be diluted with solvents as a way to lower the viscosity to help it maintain the ePTFE reinforcing material 120 (such as Donaldson D1326) which has been applied to the surface. While the ionomer solution 110A was still wet after the reinforcing material 120 was applied, the combined composite layer (ie, the wet precursor layer 115 ) drying 150 reinforced MEA (such as the first reinforced electrode and ionomer assembly 130 or the second electrode and ionomer assembly 140 ) to build. The CCDM 100A with the first electrode and ionomer assembly 130 formed a reinforced PEM layer, which then onto a second CCDM 100B was hot pressed, which only one ionomer 110B (ie no reinforcing material) coated thereon and a separate drying 150 was subjected. Depending on the ionomers, the ionomer arrangements become 130 and 140 annealed at elevated temperatures for different periods of time; this process improves the durability of the resulting MEA 170 , In the case of the two examples, the 6 and 7 Accordingly, the inventors annealed the assemblies at 140 ° C for one hour in an inert nitrogen atmosphere; this step is carried out before the hot pressing. In one form, the hot pressing conditions involved in the formation of an MEA 170 with a first CCDM 100A and a second CCDM 100E be used about 295 ° F and about 4000 pounds for about 2 minutes. The first example in conjunction with the following 6 corresponds to a substantially complete (ie anode, electrolyte and cathode) MEA 170 such as B. using the in 3 shown process, both ionomer arrangements 130 and 140 available. The second example in connection with 7 shows the results of the ionomer assembly 130 alone (comprising the ionomer solution 110B ), which in a new interim component 135 (which, for example, can be thought of as a partial MEA) is formed into, as by the in 4 shown process shown. In one form, it is not necessary to use the second CCDM 100B undergo annealing, although it is a thin layer of ionomer 105 has on it.
  • Further, cycle load tests were performed at different relative humidity (RH) without load to improve the mechanical durability of MEAs 170 to assess the membranes containing reinforced layers. In a preferred form, a first ionomer coating thickness is about 80 microns wet (which is about 6 microns dry), while a second ionomer coating thickness is additionally about 60-80 microns wet (ie 4-6 microns dry). Thus, a liquid layer applied to a thickness of 80 microns dries ionomer remaining to a thickness of 6 microns. For each test, graphite plates having an active area of 38 cm 2 with 2 mm wide straight channels and ridges were used for cell construction. The RF cycle run tests were performed at 80 ° C with ambient outlet gas pressure while introducing a constant air flow rate of 20 standard liters per minute (SLPM) into both the anode side and the cathode side of the cell in a countercurrent format. These air supplies were periodically routed or bypassed by humidifiers controlled at 90 ° C for an RF of either 150% or 0% for a duration of 2 minutes for each state. The MEA fault criteria were arbitrarily defined as 10 standard cubic centimeters per minute (SCCM) pass gas leakage from the anode to the cathode or vice versa. The RF Cycle Durability Tests (unloaded) were performed and the part showed no evidence of defect for more than 20,000 cycles. The size of the MEA made with the present invention 170 for use in the tests was set with an active area of about 38 cm 2 . As will be explained in more detail below, the tests for simulating operating conditions gave rise to those in the polarization curves of the 6 and 7 shown results.
  • The initial start-up (BOL) performance data also show similar improved results. Referring next to the 6 and 7 For example, the polarization curves are shown for two exemplary conditions. The advantage shown in these curves is that the MEAs prepared by the methods of the present invention 170 a conventional MEAs (such as the MEA 50 from 1B that a single standing PEM 15 used) achieve corresponding capacity; thus, the simplified process is compared to that used to fabricate discrete membranes, while performance related parameters (such as the load, current density, and HFR values depicted in the curve) remain substantially unaffected significantly contributes to manufacturing-related cost savings. The polarization curves are used to compare the load (voltage) and HFR as a function of the applied current density. In each figure, the upper section curves are 180 the results related to the load (left side of the Y-axis), while the lower section curves 190 correspond to the HFR results (right side of the Y-axis). For both curves 180 and 190 In both examples, there is a substantial similarity in the performance (ie both voltage and HFR) measurement results over a wide range of applied currents.
  • With special reference to 6 became in a first example the MEA 170 using the in 3 specified process produced. Specifically, a cathode version of an ionomer assembly has been used 130 containing a section of the MEA 170 makes with a Pt loading of 0.4 mg / cm 2, from 80 microns 14.4% solids Nafion ® D2020 ionomer prepared which the CCDM 100A was coated, and then becomes an ePTFE reinforcing material 120 placed on top of the coating in a manner similar to the above-mentioned paper tissue analogy. The solvent ratio of the wet ionomer was 54.3% n-propanol to 45.7% water. As mentioned above, the 80 microns wet is about 6 microns dry. Infrared (IR) furnaces set at 400 ° F for 6 minutes approximately 12 inches above the coating surface were used to dry the wet laid ionomer. Likewise, an anode version comprises an ionomer assembly 140 a CCDM 100B with a Pt loading of 0.05 mg / cm 2 and was wet with 60 micrometers (ie, dry 4 to 5 microns) of 10% solids Nafion ® D2020 ionomer with a solvent ratio of 25.3% n-propanol and 74, 7% water coated. The CCDM 100B was subjected to the same drying conditions as above for the CCDM 100A while the hot pressing conditions were as explained above.
  • With special reference to 7 Fig. 2 shows a cathode CCDM in a second example 100A a Pt loading of 0.4 mg / cm 2, as in the first example, prepared from 80 micrometers of 14.4% solids Nafion ® D2020 ionomer with an ePTFE reinforcing material 120 as explained in the previous paragraph. The solvent ratio is 54.3% n-propanol to 45.7% water. As mentioned above, the 80 microns wet is about 6 microns dry. Drying was similar to that discussed above using IR ovens. In this case, a CCDM 100A with a layer of ionomer solution 110A on an ePTFE reinforcing material 120 then again coated with 60 microns of the same 14.4% D2020 solution with the solvent ratio of 54.3 / 45.7; These steps are specifically in 4 displayed. As before, it is dried under IR at 400 ° F for 6 minutes. The CCDM 100B (which corresponds to the anode) has, as mentioned above, a Pt loading of 0.05 mg / cm 2 . Unlike the CCDM 100A Cathode was the CCDM 100B Anode with a thin ionomer coating (ie ionomer solution 110B ) so that less than about 1 micron of the ionomer is formed on the surface.
  • Thus, in the example, which 6 corresponds, relatively thick layers of ionomer solution 110A . 110B to the respective CCDMs 100A and 100B coated. These are combined during hot pressing (as a step 160 in the 3 and 4 ) (as well as 5 ), and since ionomer is present on both CCMDs, there is good adhesion. In the example, which 7 corresponds, the entire ionomer solution is on the CCDM 100A deposited. The application of a very thin ionomer layer 105 on the CCDM 100B (as in the 4 and 5 shown) helps with the subsequent hot pressing 160 to aid in contact of ionomer to ionomer for adhesion. If the thin ionomer layer 105 the CCDM 100B would not be added, would the hot pressing 160 against the ionomer from a CCDM 100A Side to an electrode surface (ie the carbon catalyst) that would not adhere well. Thus, the thin ionomer layer 105 although it is not required to be advantageous, and was for the second example of 7 used above. The drying was done with IR heating at 400 ° F for 4 minutes at a distance of about 12 inches from the thin ionomer coating 105 carried out. While the above-mentioned Pt loadings for the respective cathode and anode variants 100A and 100B As is typical in the above examples, the present inventors have studied lower cathode loadings and have observed similar performance retention.
  • Although not shown, it is preferred to use a secondary seal between the anode and the cathode and prevent electrical shorting around its edges, where anode and cathode parts cut to size with a conventional CCDM, otherwise scattered paper fibers and exposed, unprotected edges leave behind the interface, which could lead to unintentional short circuits between opposite electrode edges. As such, a secondary seal is used to cover a small portion of the edges. In examples made in accordance with the present invention, the inventors used a Kapton side seal having a thickness of 1 mil and an opening of 38 cm 2 .
  • It should be understood that terms such as "preferred," "typical," and "typically" are not used herein to limit the scope of the claimed invention or to imply that certain features are critical, essential, or even important to the structure or function of the invention claimed invention. Rather, these terms are intended merely to highlight alternative or additional features that may or may not be used in a particular embodiment of the present invention. It is also to be understood that in order to describe and define the present invention, the term "device" is used herein to represent a combination of components and individual components regardless of whether the components are combined with other components. A "device" according to the present invention may e.g. An electrochemical conversion assembly or fuel cell, as well as a larger structure (eg, a vehicle) incorporating an electrochemical conversion assembly according to the present invention. In addition, the term "substantially" is used herein to represent the natural level of uncertainty that may be associated with any quantitative comparison, value, measurement, or other representation. As such, it may represent the degree to which a quantitative representation may differ from a given reference, without resulting in a change in the fundamental function of the subject under consideration.
  • Having described the invention in detail and by reference to specific embodiments thereof, it will be apparent that modifications and variations are possible without departing from the scope of the invention as defined in the appended claims. More specifically, although some aspects of the present invention are referred to herein as preferred or particularly advantageous, it is contemplated that the present invention is not necessarily limited to these preferred aspects of the invention.

Claims (10)

  1. A method of manufacturing a membrane electrode assembly comprising: a first catalyst-coated diffusion medium is provided; and forming a reinforced polymer electrolyte membrane on the first catalyst coated diffusion media, the forming comprising: coating a first ionomer solution onto the first catalyst coated diffusion media to form a first wet ionomer layer on the surface thereof; depositing a porous reinforcement layer on the first wet ionomer layer such that the first wet ionomer layer at least partially impregnates the reinforcement layer; and drying the first wet ionomer layer with the impregnated reinforcing layer.
  2. The method of claim 1, further comprising coating a second ionomer solution on the at least partially impregnated reinforcing layer.
  3. The method of claim 1, further comprising: coating a second ionomer solution onto the second catalyst coated diffusion media to form a second wet ionomer layer on the surface thereof; the second ionomer layer is dried; and the second ionomer layer and the second catalyst-coated diffusion medium are joined to the reinforcing layer.
  4. The method of claim 3, wherein the drying of the first ionomer layer and the second ionomer layer occurs independently of each other.
  5. The method of claim 3, wherein at least one of the first and second ionomer solutions comprises an ionomer and a solvent.
  6. The method of claim 2, further comprising: disposing a second catalyst-coated diffusion media on at least one of the second ionomer solution and the at least partially impregnated reinforcing layer after the second ionomer solution has dried; and the second catalyst-coated diffusion medium and the dried second ionomer layer are joined to the reinforcing layer.
  7. A membrane electrode assembly comprising: at least one catalyst-coated gas diffusion medium; and a reinforced proton exchange membrane layer joined to the catalyst coated gas diffusion media, wherein the reinforced proton exchange membrane layer comprises a first ionomer layer with an integrated porous reinforcement layer.
  8. The membrane electrode assembly of claim 7, wherein the integrated porous reinforcement layer is made of a polymeric film, a woven fabric or a combination thereof.
  9. The membrane electrode assembly of claim 8, wherein the first ionomer layer comprises a proton conductive medium and further comprising a second ionomer layer and a second catalyst coated gas diffusion media such that the second ionomer layer is formed on a generally opposite surface of the reinforcement layer to that of the first ionomer layer.
  10. The membrane electrode assembly of claim 9, wherein the ionomer in the second ionomer layer is different than the ionomer in the first ionomer layer.
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EP3605690A1 (en) * 2018-07-30 2020-02-05 Hyundai Motor Company Method of manufacturing planar membrane electrode assembly for fuel cell and corresponding planar membrane electrode assembly for fuel cell

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US10367217B2 (en) * 2015-02-09 2019-07-30 W. L. Gore & Associates, Inc. Membrane electrode assembly manufacturing process

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US7291419B2 (en) * 2004-01-22 2007-11-06 General Motors Corporation Durable membrane electrode assembly catalyst coated diffusion media with no lamination to membrane
US8372474B2 (en) * 2006-03-13 2013-02-12 GM Global Technology Operations LLC Method of making fuel cell components including a catalyst layer and a plurality of ionomer overcoat layers
US9647274B2 (en) * 2008-01-11 2017-05-09 GM Global Technology Operations LLC Method of making a proton exchange membrane using a gas diffusion electrode as a substrate

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