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AssigneeGore Enterprise Holdings, Inc.
InventorsRobert L. Sassa, David Zuckerbrod, Wolfgang Buerger, John E. Bacino
Estimating the term…
Composite film articles and assemblies that include at least one layer of expanded fluoropolymer bonded to at least one thermoplastic sheet are fabricated using a method which can adjust the gas and liquid permeability of the composite film assemblies. These composite film articles and assemblies optionally have electroactive properties and a thin porous metallic overlayer that can serve as a current collector, and can be used in electrochemical devices such as air depolarized cells.
An electrode for an electrochemical cell comprising an electrode having an electroactive layer and a fluoropolymer composite layer, said fluoropolymer composite layer including at least one porous fluoropolymer layer and at least one discontinuous thermoplastic layer, wherein said at least one discontinuous thermoplastic layer adheres said at least one porous fluoropolymer layer to a major surface of said electroactive layer.
A method of making an electrode comprising:
The method of making an air depolarized cell comprising:
A polymeric membrane comprising an expanded fluoropolymer layer bonded to at least one thermoplastic layer, wherein the at least one thermoplastic layer is perforated in a random or a regular pattern prior to being bonded to the expanded fluoropolymer film to form a composite film.
A method of fabricating a polymeric membrane comprising:
An electrode assembly, said electrode assembly including at least one electrode containing at least a first major surface having an expanded fluoropolymer layer on said first surface, and a discontinuous layer of an adhesive.
An electrochemical cell comprising an electrode having a major contact surface and a polymer composite layer, said layer including at least one porous fluoropolymer layer and at least one discontinuous thermoplastic layer, wherein said at least one discontinuous thermoplastic layer adheres said at least one porous fluoropolymer layer to said surface.
A battery comprising an electrode with an electroactive layer that has a metal overlayer, first and second major contact surfaces, and a polymer composite layer, said layer including at least one porous fluoropolymer layer, at least one discontinuous thermoplastic layer, wherein said at least one discontinuous thermoplastic layer adheres said at least one porous fluoropolymer layer to one of said major contact surfaces.
An air depolarized cell comprising an electrode having first and second major contact surfaces and a gas diffusion membrane, said gas diffusion membrane including at least one porous fluoropolymer layer and at least one discontinuous thermoplastic layer, wherein said at least one discontinuous thermoplastic layer adheres said at least one porous fluoropolymer layer to one of said major contact surfaces.
A gas diffusion electrode that does not require a metallic screen, metallic foil, or expanded metallic foil for mechanical support or for enhancing the in-plane electrical conductivity of the electrode.
An air permeable, electrically conductive, hydrophobic composite film comprising a fluoropolymer blended with conductive carbon, wherein the composite film is bonded to a catalytically active electrode.
An air cathode for an air depolarized cell that includes a composite fluoropolymer film with an adjustable gas permeability that can be used to control the limiting current of the air depolarized cell.
An air cathode for an air depolarized cell that includes a conductive hydrophobic film with an adjustable gas permeability to control the limiting current of the air depolarized cell.
Dependencies are inferred from the claim text.
From the US filing history. Foreign family members aren’t listed.
Backward citations are indexed for grants only.
Composed of a half-cell of the fuel-cell type and of a half-cell of the primary-cell type: with one metallic and one gaseous electrode
Inert electrodes with catalytic activity, e.g. for fuel cells: porous electrodes
Inert electrodes with catalytic activity, e.g. for fuel cells: non-porous diffusion electrodes, e.g. palladium membranes, ion exchange membranes
Electrical device making: electric battery cell making
Term end not estimated
This invention relates to thin fluoropolymer/thermoplastic resin composite films, their manufacture, and uses thereof. More specifically, the present invention relates to composite film assemblies which are bonded durably to each other and can include a membrane separator, at least one electroactive layer, an ultrathin conductive metal layer, and a hydrophobic gas permeable membrane which can serve to modulate the gas permeability while preventing liquid permeation of the composite film.
Electrochemical devices such as zinc/air primary batteries and nickel/hydrogen satellite batteries use barrier materials and/or gas diffusion membranes. Often the required permeability of these films to gases or vapors varies depending on the intended use, and can range from microporous, high flow-rate, membranes to very dense, (almost full density) fluoropolymer membranes (as in air depolarized cells). This range of permeabilities is typically realized by choosing membranes with different pore sizes and/or porosities.
Gas diffusion membranes have been used with gas diffusion electrodes at the anode, cathode, or both. For instance, a nickel-hydrogen battery uses a hydrogen electrode, the zinc-air battery uses an oxygen electrode, and the alkaline fuel cell uses both. The main advantages to using a gas diffusion electrode are that the reagents necessary for the electrochemical reaction can be stored outside the immediate electrochemical cell (as in the case for the hydrogen electrode) or absorbed from the environment (as in the case of the oxygen electrode). In particular, the zinc-air battery has an energy density of about twice that of an alkaline zinc-manganese dioxide battery because only the zinc needs be stored within the battery. Oxygen for the cathode reaction is supplied from the ambient air.
FIG. 1 is a cut-view diagram of a metal/air cell. (From The Handbook of Batteries, by David Linden, Second Edition, McGraw-Hill, Inc. 1994).
FIG. 2 is a schematic diagram of an electrode assembly using a conductive gas diffusion membrane, as described in one embodiment of the present invention.
FIG. 3 is a schematic diagram of air electrode with conductive gas diffusion layer and non-conductive air distribution layer, as described in one embodiment of the present invention.
The gas diffusion membrane of the present invention is used in electrochemical devices, and in particular in an air depolarized cell. The membrane is formed from a porous fluoropolymer layer that is thermally bonded to a thermoplastic material, subjected to a thermal expansion and cooled. A suitable expanded polytetrafluoroethylene (ePTFE) material is the nonwoven ePTFE films disclosed by Bowman in U.S. Pat. No. 4,598,011, by Branca in WO 96/07529 and by Bacino in U.S. Pat. No. 5,476,589, the contents of which are incorporated herein by reference. The ePTFE films described therein are extremely thin, strong, chemically inert and intrinsically can have a high air flow-through rate.
Suitable fluoropolymers for making ePTFE films include PTFE and PTFE copolymers. The PTFE can also be a type of PTFE with co-monomers, referred to as “modified PTFE”. This designation also covers polymers in which the homopolymer is modified by copolymerization with ethylenically unsaturated co-monomers, their share being <2 mass percent based on the copolymer. Examples of such co-monomers include the following: ethylene, propylene, halogenated olefins such as hexafluoropropylene, vinylidene fluorides and chlorotrifluoroethylene; cyclic fluorinated monomers or perfluoroalkylvinylethers such as perfluoropropylvinylethers, perfluoromethylvinylethers or perfluorobutylether. If the proportion of copolymer is more than 2 mass percent, the fluoropolymers are typically referred to as fluorothermoplastics or fluoroelastomers.
Other suitable starting raw materials include fluorinated homopolymers. Fluorinated homopolymers can be present as blends with low-molecular PTFE or blends with modified PTFE. The fluorinated homopolymers are likewise mixable with tetrafluoroethylene (TFE) copolymers processed from the melt, such as hexafluoropropylene/tetrafluoroethylene copolymers (FEP), perfluoroalkylvinyl/tetrafluoroethylene copolymers (PFA) or perfluorodioxol copolymers, such as those available under the brand name Teflon AF from Dupont. The use of fluorothermoplastics is disclosed by Gleinser in U.S. Pat. No. 6,127,486.