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US-12617193-B2 - Electrically conductive corrosion resistant bodies of low permeability

US12617193B2US 12617193 B2US12617193 B2US 12617193B2US-12617193-B2

Abstract

An electrically conductive, corrosion resistant carbon-based sheet with low permeability to liquids and gases and a method for its manufacture. A multilayer laminate consisting of polymeric film laminated with expanded graphite foil is produced by compressing the layers under heated conditions. The resulting laminate can be used to produce a current collector or a bipolar layer in an electrochemical cell.

Inventors

  • Jay Dandrea

Assignees

  • Jay Dandrea

Dates

Publication Date
20260505
Application Date
20230912

Claims (13)

  1. 1 . A laminated body, consisting of: a first layer of polymer film, a first layer of graphite foil, and wherein the first layer of graphite foil is in direct contact with the first layer of polymer film, and wherein the first layer of graphite foil is laminated to the first layer of polymer film, such that individual flakes of the graphite foil pierce the polymer film, thereby rendering the laminated body electrically conductive in a through-plane direction and substantially impermeable to air.
  2. 2 . The laminated body of claim 1 , wherein the first layer of polymer film comprises an electrically conductive filler.
  3. 3 . The laminated body of claim 1 , wherein the first layer of polymer film comprises an electrically conductive filler and polyethylene.
  4. 4 . The laminated body of claim 1 , wherein the first layer of polymer film comprises an electrically conductive carbon filler and polyethylene.
  5. 5 . The laminated body of claim 4 , wherein the mass density of the laminated body is between 1.03 g/cm3 and 1.51 g/cm3.
  6. 6 . The laminated body of claim 1 , wherein the mass density of the laminated body is between 1.03 g/cm3 and 1.51 g/cm3.
  7. 7 . A laminated body, comprising: a first layer of polymer film, a first layer of graphite foil, and a second layer of polymer film, wherein the first layer of graphite foil is in direct contact with each of the first layer of polymer film and the second layer of polymer film, and wherein the first layer of graphite foil is laminated between the first layer of polymer film and the second layer of polymer film, such that individual flakes of the graphite foil pierce the first and second polymer films, thereby rendering the laminated body electrically conductive in a through-plane direction and substantially impermeable to air.
  8. 8 . The laminated body of claim 7 , wherein the first layer of polymer film comprises an electrically conductive filler.
  9. 9 . The laminated body of claim 7 , wherein the first layer of polymer film comprises an electrically conductive filler and polyethylene.
  10. 10 . The laminated body of claim 7 , wherein the first layer of polymer film comprises an electrically conductive carbon filler and polyethylene.
  11. 11 . The laminated body of claim 10 , wherein the mass density of the laminated body is between 1.03 g/cm3 and 1.51 g/cm3.
  12. 12 . The laminated body of claim 7 , wherein the mass density of the laminated body is between 1.03 g/cm3 and 1.51 g/cm3.
  13. 13 . The laminated body of claim 7 , wherein the first and second layers of polymer film are electrically insulating.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is based on claims priority to U.S. patent application Ser. No. 17/752,484 filed May 24, 2022 entitled “ELECTRICALLY CONDUCTIVE CORROSION RESISTANT BODIES OF LOW PERMEABILITY”. FIELD OF THE INVENTION This invention relates to an electrically conductive sheet of low permeability made of a laminate comprised of one or more layers of expanded graphite foil and one or more layers of a polymeric film, a process for producing such a film, and a component for an electrochemical device. BACKGROUND OF THE INVENTION In an electrochemical device of monopolar design multiple anode-cathode pairs are connected in parallel by a connection outside of the active area of the cell. Multiples of these cells are then connected in series to increase the voltage of the device to the level required by the application. In a bipolar design, individual cells are stacked directly adjacent one another to increase voltage. The discrete cells are separated by a component known as the bipolar layer. Bipolar construction can be applied to any type of electrochemical device, such as batteries, fuel cells, electrolyzers, or flow batteries, and has the potential advantages of being more compact, lighter, cheaper, and having lower internal resistance than an energy equivalent device of monopolar design. A challenge encountered when designing devices of bipolar design comes in the form of the bipolar layer. For the bipolar layer to effective, it must have good electronic conductivity, but be impermeable to ions and gases. Additionally, the material must be electrochemically stable at both anodic and cathodic potentials. Few materials meet these requirements, and solutions to the bipolar layer problem have historically been elaborate and expensive. Materials currently used for bipolar layers are typically either metals or carbon-based. Metals are attractive due to their higher specific electrical conductivity, high strength, and their ability to be formed by conventional means such as stamping, but are susceptible to corrosion. More corrosion resistant metals such as titanium and stainless steel are expensive, more difficult to process, and still often require coatings to slow the corrosion rate, and while the materials themselves may be of high conductivity, these coatings tend to introduce a high contact resistance between the bipolar layer and the gas diffusion layer of a fuel cell or the electrode of a battery. Graphite is inert to most chemical reactions and has good electrical conductivity, making it a suitable candidate for a bipolar layer. Recompressed expanded graphite is preferred over solid graphite as a material for a bipolar layer as it can be more easily formed, is of lower cost and possesses better mechanical properties. A typical process for producing recompressed flexible graphite foil is described in U.S. Pat. No. 3,404,061. This method involves mixing natural graphite flakes with an oxidizing agent and then subjecting the mixture to high heat, which causes the graphite flakes to expand. When the expanded graphite flakes are then recompressed, the individual flakes of the expanded graphite interlock with one another resulting in a flexible foil. However, as bodies made from recompressed expanded graphite are inherently porous, additional processing is required in order to make them impermeable to liquids and gases. The porosity of expanded graphite-based bodies has traditionally been removed by vacuum impregnation of the body with a resin. As the resin only fills in existing voids in the material, the electrical conductivity of the impregnated material is comparable to the previously porous foil. U.S. Pat. No. 4,729,910 describes a method for impregnating flexible expanded graphite sheet with a liquid thermosetting resin in the interest of improving mechanical strength and reducing gas permeability. A similar process is described in U.S. Pat. No. 6,746,771, wherein the resulting impregnated sheet has the application of a bipolar plate for a fuel cell. These impregnation processes have the disadvantage of being slow and requiring large capital investments, and as such, the resulting product is of considerable cost. It is an object of this invention to produce a laminated material comprised of alternating layers of expanded graphite sheet and polymeric film which has bulk properties of electrical conductivity and low permeability comparable to that of resin impregnated expanded graphite at a greatly reduced cost. Methods of laminating expanded graphite sheets have been described previously. U.S. Pat. No. 3,404,061 details laminating two superposed flexible graphite sheets with a strengthening layer of a dissimilar material interposed between the two sheets using an adhesive such as tar, carbon cement, or thermoset resin. U.S. Pat. No. 5,128,209 describes a composite gasket material comprised of alternating layers of expanded graphite sheet and a porous fluoropolymer film in