Concentrated electrolytes: decrypting electrolyte properties and reassessing Al corrosion mechanisms

• DOI: 10.1039/c3ee42351d
• Publication Date: 2013-10-30T10:37:16Z
• Authors: Dennis W. McOwen; Daniel M. Seo; Oleg Borodin; Jenel Vatamanu; Paul D. Boyle; Wesley A. Henderson
• Keywords: Diethyl carbonate

Highly concentrated electrolytes containing carbonate solvents with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) have been investigated to determine the influence of eliminating bulk solvent (i.e., uncoordinated a Li+ cation) on electrolyte properties. The phase behavior ethylene (EC)–LiTFSI mixtures indicates that two crystalline solvates form—(EC)3:LiTFSI and (EC)1:LiTFSI. Crystal structures for these were determined obtain insight into ion coordination. Between compositions, however, crystallinity gap exists. A Raman spectroscopic analysis EC bands 3–1 2–1 EC–LiTFSI liquid ∼86 95%, respectively, is coordinated cations. This extensive coordination results in significantly improved anodic oxidation thermal stabilities as compared more dilute 1 M) electrolytes. Further, while extensively corrode Al current collector at high potential, do not. new mechanism corrosion Li-ion batteries proposed explain this. Although ionic conductivity somewhat low relative state-of-the-art formulations used commercial batteries, using an EC–diethyl (DEC) mixed instead pure markedly improves conductivity.