TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Polyelectrolyte: The alkali metal salt is at least lithium perchlorate (LiClO4), lithium tetrafluoro borate (LiBF4), lithium hexafluoro phosphate (LiPF6) and/or LiN(CF3SO2)2.    TECHNOLOGY FOCUS - POLYMERS - Preferred Substances: The acrylic resin is synthesized by constructing a polymer frame work with (A) component monomer, (B) component monomer and methacrylate monomer (C') which has a hydroxyl group. The hydroxyl group of polymer main chain is reacted with methacrylate monomer (C) which has isocyanate group of the same number of moles as the hydroxyl group of polymer main chain, so that the polymer main frame may have a (meth)acryloyl group in the side chain. EXAMPLE - (In weight parts) Blend material (I) comprising n-butyl acrylate (57), ethyl acrylate (15), acrylonitrile (26), 2-hydroxyethyl acrylate (2) and methylethyl ketone (MEK) (30) was heated to 90-95degreesC. Blend material (II) comprising azobisisobutyronitrile (0.1) and MEK (5) was added to the heated mixture and further heated for 2-5 hours. Subsequently, blend material (III) comprising t-butyl peroxybenzoate (0.5) and MEK (20) was added for 2 hours and heat retention was carried out for 3-6 hours. The mixture was cooled and blend material (IV) comprising 2-isocyanatoethyl methacrylate (2.5) and MEK (5) was added to the polymer solution and heated for 70-75degreesC for 6-12 hours. Methanol was added and the polymer was allowed to settle after cooling. The organic solvent was removed by suction filtration, vacuum dried and acrylic resin (A) with molecular weight of 250000 was obtained. Methyl ethyl ketone solution of acrylic resin (A) was cross-linked with trimethylol propoane trimethacrylate (5) and benzoyl peroxide (0.1) was added as polymerization initiator. The resulting mixture was applied on a Teflon support and dried for 20 minutes at 80degreesC. Thermal polymerization was carried out for 3 hours at 100degreesC under vacuum. The polymer film formed had thickness of 50 mum. The film was made to swell by an electrolyte mixture containing ethylene carbonate, lithium hexafluoro phosphate and dimethyl carbonate and a polyelectrolyte was synthesized. The obtained polyelectrolyte had ionic conductivity of 1.8x10-3 S/cm at 25degreesC, fracture strength of 1.5 MPa and modulus of elongation of 1.8 MPa.