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Self-Passivating Lithium/Solid Electrolyte/Iodine CellsRobust lithium/solid electrolyte/iodine electrochemical cells that offer significant advantages over commercial lithium/ iodine cells have been developed. At room temperature, these cells can be discharged at current densities 10 to 30 times those of commercial lithium/iodine cells. Moreover, from room temperature up to 80 C, the maximum discharge-current densities of these cells exceed those of all other solid-electrolyte-based cells. A cell of this type includes a metallic lithium anode in contact with a commercial flexible solid electrolyte film that, in turn, is in contact with an iodine/ graphite cathode. The solid electrolyte (the chemical composition of which has not been reported) offers the high ionic conductivity needed for high cell performance. However, the solid electrolyte exhibits an undesirable chemical reactivity to lithium that, if not mitigated, would render the solid electrolyte unsuitable for use in a lithium cell. In this cell, such mitigation is affected by the formation of a thin passivating layer of lithium iodide at the anode/electrolyte interface. Test cells of this type were fabricated from iodine/graphite cathode pellets, free-standing solid-electrolyte films, and lithium-foil anodes. The cathode mixtures were made by grinding together blends of nominally 10 weight percent graphite and 90 weight percent iodine. The cathode mixtures were then pressed into pellets at 36 kpsi (248 MPa) and inserted into coin-shaped stainless-steel cell cases that were coated with graphite paste to minimize corrosion. The solid-electrolyte film material was stamped to form circular pieces to fit in the coin cell cases, inserted in the cases, and pressed against the cathode pellets with polyethylene gaskets. Lithium-foil anodes were placed directly onto the electrolyte films. The layers described thus far were pressed and held together by stainless- steel shims, wave springs, and coin cell caps. The assembled cells were then crimped to form hermetic seals. It was found that the solid electrolyte films became discolored within seconds after they were placed in contact with the cathodes - a result of facile diffusion of iodine through the solid electrolyte material (see figure).
Document ID
20110013625
Document Type
Other - NASA Tech Brief
Authors
Bugga, Ratnakumar
(California Inst. of Tech. Pasadena, CA, United States)
Whitcare, Jay
(California Inst. of Tech. Pasadena, CA, United States)
Narayanan, Sekharipuram
(California Inst. of Tech. Pasadena, CA, United States)
West, William
(California Inst. of Tech. Pasadena, CA, United States)
Date Acquired
August 25, 2013
Publication Date
December 1, 2006
Publication Information
Publication: NASA Tech Briefs, December 2006
Subject Category
Man/System Technology And Life Support
Report/Patent Number
NPO-40789
Distribution Limits
Public
Copyright
Public Use Permitted.
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