The interfacial properties of the lithium electrode in contact with a solvent plasticized polymer electrolyte have been probed by ac and de impedance methods. The behavior and nature of this interface layer were characterized, under both static (open circuit) and dynamic (cell cycling) conditions, Measurements have been carried out primarily in symmetrical Li/Li and Li/V6O13 cells, some of which had incorporated a suitable reference electrode. Due to the PC/LiAsF6 content of the polymeric electrolyte, a conductivity exceeding 1 mS/cm at room temperature was achieved. The initial Li/V6O13 cell impedance was shown to be strongly dominated by the pristine layer present on the lithium. During passage of charge through the layer, disruption of the layer occurs as evidenced by the simultaneously decreasing cell impedance. A new layer is formed by reaction between the electrolyte components and the lithium metal. During the first few cycles, the impedance of the lithium electrode gradually decreases. This is presumably caused by a gradual increase in electrode surface area due to roughening of the lithium surface.