Compositions – Electrically conductive or emissive compositions – Elemental carbon containing
Reexamination Certificate
1999-02-08
2001-12-25
Gupta, Yogendra N. (Department: 1751)
Compositions
Electrically conductive or emissive compositions
Elemental carbon containing
C252S503000, C429S047000, C502S180000, C502S182000, C423S44500R
Reexamination Certificate
active
06332990
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is directed to the use of aerogels, particularly to carbon aerogel electrodes, and more particularly to a composite carbon foam electrode and method of fabrication wherein solid carbon, carbon aerogel, or metal particles are added during the process.
Aerogels, carbon aerogels, and carbon foams have been produced by various methods for a variety of applications. These prior processes are exemplified by U.S. Pat. No. 4,806,290 issued Feb. 21, 1989 to R. W. Hopper et al; U.S. Pat. No. 4,873,218 issued Oct. 10, 1989 to R. W. Pekala; U.S. Pat. No. 4,997,804 issued Mar. 5, 1991 to R. W. Pekala; U.S. Pat. No. 5,086,085 issued Feb. 4, 1992 to R. W. Pekala; and U.S. Pat. No. 5,252,620 issued Oct. 12, 1993 to J. R. Elliott, Jr. et al. Recently, efforts have been directed to the development of carbon foams for use as electrodes and include all forms of carbon foams, monolithic, granular or microspheres. Such electrodes find use in energy storage devices, i.e. capacitors and batteries, as well as for fuel cells and electrocapacitive deionization devices, etc. These efforts are exemplified by U.S. Pat. No. 5,260,855 issued Nov. 9, 1993 to J. L. Kaschmitter et al., and copending U.S. application Ser. No. 08/036,740 filed Mar. 25, 1993, entitled “Carbon Foams For Energy Storage Devices”, now U.S. Pat. No. 5,529,971 issued Jun. 25, 1996; Ser. No. 08/041,503 filed Apr. 1, 1993, entitled “Method Of Low Pressure And/Or Evaporated Drying Of Aerogel”, now U.S. Pat. No. 5,420,168 issued May 20, 1995 and Ser. No. 08/089,119 filed Jul. 8, 1993, entitled “Organic Aerogel Microspheres And Fabrication Method Therefor”, now U.S. Pat. No. 5,508,341 issued Apr. 16, 1996.
It has been discovered by the present invention that manufacturability and performance of these prior carbon foams for electrode applications can be enhanced by using these prior materials as particles with a carbon foam binder to form a composite electrode. Manufacturability would be enhanced by allowing precursor materials to be spread in very thin films or as thin films on roll to roll substrates. Also, performance could be further enhanced by mixing other high performance carbons, in particulate form with the precursor, prior to firing. Thus, this invention provides a composite carbon foam electrode and method for fabricating same.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a carbon foam electrode.
A further object of the invention is to provide a composite carbon foam electrode.
A further object of the invention is to provide a method for fabricating composite carbon foam electrodes.
Another object of the invention is to provide a composite carbon foam electrode having therein granularized materials including other forms of carbon and metal additives, such as carbon microsphere, carbon foam particles, carbon powders, and carbon and/or metal fibers.
Another object of the invention is to provide a method for producing composite carbon foam electrodes which involves a modification of prior known methods by adding granularized materials during the phase of the process that the precursor materials are still liquids (i.e. prior to gelation), and allowing the precursor materials to be spread in very thin films on roll to roll substrates.
Other objects and advantages will become apparent from the following description and accompanying drawing. Basically, the invention comprises a composite carbon foam electrode in which is incorporated granularized materials and a method of fabricating same. Choice of materials and fibers to be used in the composite electrode will depend on the electrolyte used and the relative trade off of system resistivity and power to system energy. Metal and/or carbon fibers may be added for increased conductivity, such may include nickel, stainless steel, aluminum, carbon, electroplated carbon fiber, etc. The granularized materials, solid particles, or microspheres added to the precursor materials may include: 1) carbon aerogel microspheres, 2) crushed/powderized carbon aerogel, 3) powderized activated or non-activated carbon or any other source type, and 4) metal and/or metal oxide powders or spheres. The method for fabrication is generally similar to the methods of the above referenced patents and copending applications except that the granularized materials are added during the phase where the precursor materials are liquid (prior to gelation), and the precursor materials are spread in very thin films or as thin films on roll to roll substrates. The simplicity of manufacture over monolithic carbon aerogel production is significant. Improved capacities per volume and per weight may be achieved by applying this method when compared to thin film casting onto composite substrates. Performance could be further enhanced by mixing other high performance carbons, in particulate form, with the precursor, prior to pyrolysis.
REFERENCES:
patent: 4626612 (1986-12-01), Brotz
patent: 4832881 (1989-05-01), Arnold, Jr. et al.
patent: 4873218 (1989-10-01), Pekala
patent: 5358802 (1994-10-01), Mayer et al.
Kaschmitter James L.
Mayer Steven T.
Pekala Richard W.
Carnahan L. E.
Gupta Yogendra N.
Hamlin D. G.
The Regents of the University of California
Thompson Alan H.
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