Solid polymer electrolytes have been prepared consisting of magnesium or zinc trifluoromethanesulfonates [Mg(CF3SO3)(2) or Zn(CF3SO3)(2)], ethylene carbonate, and propylene carbonate included in a photo-crosslinked polymer of poly-(ethylene glycol) diacrylate and reinforced by a porous polypropylene membrane. Their conductivities are 1.7 x 10(-4) S cm(-1) at 1 mol% for Mg(CF3SO3)(2), 2.1 x 10(-4) S cm(-1) at 4 mol% for Zn(CF3SO3)(2), and 4.3 x 10(-4) S cm(-1) at 12 mol% for LiCF3SO3 systems at 25 degrees C. Their Arrhenius plots are almost linear between -5 and 55 degrees C with 15-25 kJ mol(-1) activation energy for conduction.