The passivation phenomena at the lithium-gel polyelectrolyte interface were examined by means of the impedance spectroscopy and the de polarization of cells. Polymeric lithium salts with immobilized carboxylic anions, plasticized with dimethoxyethylenesulfoxide, were used as the electrolyte. It was found that passivation layers could be formed in these systems both on the surface of the electrode and the polymeric membrane. The generation of mobile anions and decrease of the lithium transference number accompany the passivation. The passivation undergoes strong inhibition in the presence of BF3.