TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Compounds: The second lithium salt is selected from LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, LiC4F9SO3, LiAlO4, LiAlCl4, and lithium bis(oxalato)borate (preferably lithium bis(oxalato)borate).    TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The polyether block is polyethylene oxide. The acrylate block is methylmethacrylate. The acrylate block is a random copolymer. The diblock copolymer is a poly(ethylene oxide) (PEO)-b-polymethylmethacrylate (PMMA) block copolymer. The molecular weight ratio of PEO to PMMA is 4:1 to 10:1. The lithium salt of the diblock copolymer is a lithium salt of an acrylic acid (preferably methacrylic acid). The lithium salt of diblock copolymer is PEO-b-(PMMA-ran-PMAALi). The ratio of the diblock copolymer to the second lithium salt is 65-95% ethylene oxide unit to 35-5% second lithium salt. The ratio of the diblock copolymer to the second lithium salt is 75% (preferably 80%) ethylene oxide unit to 25% (preferably 20%) second lithium salt. The lithium ions of the lithium salt of the diblock copolymer are incorporated within the microphase separated spherical domains of the acrylate block. Preferred Method: In the method, the diblock copolymer salt solution is produced by adding a mixture of 1,4-dioxane and methanol. The method further involves casting the polymer solution into an apparatus containing a substrate; and drying the polymer solution to produce a polymer electrolyte film. EXAMPLE - Lithium bis(oxalato)borate (LiBOB) salt was added to PEO-b-(PMMA-ran-PMAALi) to formed polymer solution. Tetrahydrofuran (THF) was used as the solvent, which was degassed using multiple cycles of a freeze-pump-thaw method. The polymer solutions were then cast into petri-dishes containing molds of poly(tetrafluoroethylene) (PTFE)-coated aluminum sheets. The polymer solutions were dried over several days resulting in 200-250 mu m thick polymer electrolyte films. Due to high charge density, lithium batteries using the solid electrolyte polymers shows high performance with a nominal voltage over 3.6 volts. The solid electrolyte polymer circumvents the use of corrosive and flammable liquid based electrolytes, thus provides for the creation of safe and flexible energy sources; shows potential for the design of ultrathin batteries as thin (if not thinner) than 0.4 mm. The solid electrolyte polymers are more compatible with battery electrodes than conventional inorganic glass or ceramic electrolytes and exhibits minimal capacity fade over 500 cycles, hence has longer performance life than conventional inorganic glass or ceramic electrolytes.