Analysis of surface films on lithium in various organic electrolytes

The surface films formed on lithium metal in ethylene carbonate (EC) + dimethyl carbonate (DMC) containing LiPF6, LiClO4 and LiN(SO2CF3)2 electrolytes were analysed by using Auger electron spectroscopy (AES), temperature-programmed decomposition mass spectrography (TPD-MS), FT-IR, ion chromatography (IC) and atomic adsorption spectroscopy (AAS). The morphology of the film was observed by using scanning electron microscopy (SEM). The film formed in the LiPF6 solution exhibited spherical morphology and was found to contain LiF, lithium oxide compounds (most of which seems to be inorganic), (CH2OCO2Li)2 and CH3OCO2Li. The films in LiClO4 and LiN(SO2CF3)2 were dendritic and contained the lithium oxide compounds, (CH2OCO2Li)2 and CH3OCO2Li.