The electrochemical quartz crystal microbalance (EQCM) and cyclic voltammetry have been applied simultaneously to characterize electron-beam deposited carbon film electrodes in LiClO4-containing mixed electrolytes of ethylene carbonate (EC) and dimethyl carbonate (DMC). The structure of the carbon electrode was found to be amorphous/disordered using Raman spectroscopy. Cyclic voltammetry in LiClO4/EC + DMC demonstrated features typical of Li intercalation/deintercalation into/from the disordered carbon electrode, and EQCM showed a corresponding mass increase/decrease. Combined EQCM and spectroscopic ellipsometry data were compared, and the solid electrolyte interphase density after the first cycle in LiClO4/EC + DMC was estimated to be 1.3 g/cm(3). (C) 2003 The Electrochemical Society.