Stability of Aluminum in Low-Temperature Lithium-Ion Battery Electrolytes

Report No. ARL-TR-1879
Authors: Behl, Wishvender K.; Plichta, Edward J.
Date/Pages: March 1999; 17 pages
Abstract: We investigated the stability of aluminum at the high positive potentials encountered during the charging of lithium-ion cells. The electrolyte in these cells consists of solutions of lithium hexafluorophosphate and lithium methide in binary- and ternary-solvent mixtures of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate. We performed the investigations with the controlled potential coulometry technique. We found that a protective surface film was formed on aluminum electrodes in these solutions and that this film protected the electrodes from further corrosion. The protective surface film was found to break down in lithium methide solutions at 4.25 V versus a lithium reference electrode, and this resulted in increased corrosion of the aluminum electrodes at higher potentials. In contrast to lithium methide solutions, the protective surface film formed on aluminum electrodes in lithium hexafluorophosphate solutions was found to be quite stable and did not break down at potentials up to ^5 V.
Distribution: Approved for public release
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Last Update / Reviewed: March 1, 1999