M. Mori et al., MODIFICATION OF THE LITHIUM METAL-SURFACE BY NONIONIC POLYETHER SURFACTANTS - QUARTZ-CRYSTAL MICROBALANCE STUDIES, Journal of the Electrochemical Society, 145(7), 1998, pp. 2340-2348
Citations number
37
Categorie Soggetti
Electrochemistry,"Materials Science, Coatings & Films
In order to stabilize and obtain highly ion-conductive surface films,
lithium metal was modified using two kinds of nonionic polyether-type
surfactants, viz., poly(ethylene glycol) dimethyl ether and dimethyl s
ilicone/propylene oxide copolymer in propylene carbonate (PC) and ethy
lene carbonate (EC) + dimethyl carbonate (DMC) solutions. Impedance sp
ectroscopy indicated that the surface films formed in the presence of
these surfactants were very stable, whereas that in the absence of sur
factant was not. Scanning electron microscopy images showed that local
ized deposition is suppressed for the modified systems compared with t
he unmodified system. The mass change associated with the deposition-d
issolution of lithium was investigated with cyclic voltammetry (CV) an
d quartz crystal microbalance (QCM) methods. The CV/QCM analyses indic
ated that the extent of inactive lithium is diminished markedly (by ca
. 50% for PC and ca. 30% for EC + DMC solutions) and that the surface
film was very stable and its thickness was apparently invariant due to
the presence of the surfactants on the electrode surface. The QCM ana
lysis also suggested that the surface-film may partly consist of the s
urfactant molecule constituents, including ethylene oxide (EO) groups
reacted with lithium metal. It appears that a modified surface film in
cluding EO chains enhances the ionic conductivity, surface uniformity,
and cyclability.