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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 22, Number 5
BKCSDE 22(5)
May 20, 2001 

 
Title
Characterization of Surface Films Formed Prior to Bulk Reduction of Lithium in Rigorously Dried Propylene Carbonate Solutions
Author
Seok-Gyun Chang, Hyo Joong Lee, Heon Kang, Su-Moon Park
Keywords
Surface films, Passivation, Lithium reduction, Propylene carbonate, Electrochemical quartz crystal microbalance, Secondary ion mass spectrometry.
Abstract
Surface films formed prior to bulk reduction of lithium have been studied at gold, platinum, and copper electrodes in rigorously dried propylene carbonate solutions using electrochemical quartz crystal microbalance (EQCM) and secondary ion mass spectrometry experiments. The results indicate that the passive film formation takes place at a potential as positive as about 2.0 V vs. Li/Li+ , and the passive film thus formed in this potential region is thicker than a monolayer. Quantitative analysis of the EQCM results indicates that electrogenerated lithium reacts with solvent molecules to produce a passive film consisting of lithium carbonate and other compounds of larger molecular weights. The presence of lithium carbonate is verified by SIMS, whereas the lithium compounds of low molecular weights, including lithium hydroxide and oxide, are not detected. Further lithium reduction takes place underneath the passive film at potentials lower than 1.2 V with a voltammetric current peak at about 0.6 V.
Page
481 - 487
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