The interphases formed on Li electrodes in various propylene carbonate solutions were investigated using impedance spectroscopy. The influences of temperature and solution composition (salt, concentration, additive and contaminants) were studied. The data obtained were modelled by equivalent circuit analogues of five RC sections in series. Calculations based on various experiments indicate that the various RC sections in this equivalent circuit analogue were related to different layers which constitute the Li-solution interphase. It was possible to calculate thickness and resistivity of the various layers based on the assumption that changes in the composition and structure of the surface films strongly affected their resistivity but not their relative permittivity, because the permittivity of the various surface species formed on Li are very similar. This calculation seemed to show that the interphase changes considerably in its structure and electrical properties from Li to the solution.