Modification of Lithium Metal Surface by Non-ionic Polyether Surfactant: Quartz Crystal Microbalance Studies

摘要

In order to stabilize and get highly ion-conductive surface film, lithium metal has been attempted to modify using two kinds of non-ionic polyether type surfactants, viz., poly(ethylene glycol) dimethyl ether (PEGDME), dimethyl silicone/propylene oxide copolymer (SiPPO). A mass change associated with the deposition and dissolution of lithium with surface modification by these was investigated with quartz crystal microbalance (QCM) method. The experiment was carried out in some representative solvents like propylene carbonate (PC) and ethylene carbonate (EC)+dimethyl carbonate (DMC) solutions. QCM analysis indicated that with such modification the extent of electrochemical inactivation is remarkably diminished by ca. 50 % for PC, and ca. 30 % for EC+DMC solutions. The increased M_(eq)~1 value (70-130 g mol~(-1)rn) for surfactant modified systems compared to unmodified systems (M_(eq) = 25-35 g mol~(-1)), suggested that the surface filmrnconsists of the fraction of surfactant molecule which helped to enhance the ionic conductivity, surface uniformity, and cycleability.