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Method of producing less anisotropic flexible graphite

United States Patent Application

View the Complete Application at the US Patent & Trademark Office
This invention provides a method for recompressing expanded or exfoliated graphite to produce a less anisotropic, flexible graphite foil having a thickness-direction electrical conductivity no less than 15 S/cm. In one preferred embodiment, the method comprises: (a) providing a mixture of expanded or exfoliated graphite flakes and particles of non-expandable graphite or carbon, wherein the non-expandable graphite or carbon particles are in the amount of between about 3% and 70% by weight based on the total weight of the particles and the exfoliated graphite; (b) compressing the mixture in at least a first direction to a pressure within the range of from about 0.04 MPa to about 350 MPa into a first cohered mixture; and (c) compressing this first cohered mixture in a second direction, different from the first direction, to a pressure sufficient to produce said flexible graphite foil having a bulk density within the range of from about 0.1 g/cm.sup.2 to about 2.0 g/cm.sup.2. All these operations are preferably conducted continuously. The foil exhibits a thickness-direction conductivity typically greater than 50 S/cm, more typically greater than 100 S/cm, and most typically greater than 200 S/cm. The foil can be used as a component in a sheet molding compound plate as a fuel cell separator or flow field plate. The foil may also be used as a current collector for a battery, supercapacitor, or any other electrochemical cell.
Zhamu, Aruna (Centerville, OH), Shi, Jinjun (Columbus, OH), Guo, Jiusheng (Centerville, OH), Jang, Bor Z. (Centerville, OH)
11/ 899,008
September 4, 2007
[0001] This invention is based on the research results of a project supported by the US Department of Energy (DOE) SBIR-STTR Program. The US government has certain rights on this invention.