A mixture of flammable organic solvent, alkali metal salt, and nonflammable room temperature ionic liquid has been used as a new type of electrolyte. A novel microporous polymer electrolyte based on poly(vinylidene fluoride), i.e., PVDF, and polyethylene glycol), i.e., PEG, was prepared by a simple phase-inversion technique. The mixed electrolyte was observed to be nonflammable at ionic liquid contents of 60 vol % or greater. The viscosity (range, 0.98-30.5 mPa s) and conductivity (range, 9.9 to 22.25 mS cm(-1)) of the mixed electrolyte were discussed. The porosity, solution uptake, and conductivity mechanism of polymer membranes also here discussed. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 113: 2492-2498, 2009