A new methodology to obtain single-ion-conducting polymer electrolytes is proposed. A polymeric salt, lithium salt of poly(2-oxo-1-difuluoroethylene sulfonylimide) (LiPI), has a structure resembling recently developed highly dissociable imide salts such as lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) and is considered as their polymer analogue. The polymer salt is expected to dissociate in an organic solvent and even in a polyether solvent, and to exhibit similar electrochemical stability to LiTFSI. Polymer electrolytes were prepared by dissolving LiPI in polyether networks to afford a compatible polymer alloy. Lithium transference number of the polymer electrolytes was found to be unity, though the ionic conductivity was not sufficiently high. The conductivity greatly increased by adding a highly polar solvent, ethylene carbonate, to the polymer alloy electrolytes. (C) 2000 Elsevier Science Ltd. All rights reserved.