TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Compounds: The cyclic carboxylate ester is chosen from gamma-butyrolactone and/or gamma-valerolactone. The electrolyte further contains ethylene carbonate and/or propylene carbonate as solvent. Preferred Properties: The composition of electrolyte is expressed as a tetragon with vertices (A-D) in a triangular figure, when the amount (in mass ratio) of ethylene carbonate or propylene carbonate, gamma-butyrolactone and ethylene carbonate, are plotted on x-z axis respectively, where A is (0.55,0.25,0.2), B is (0.35,0.25,0.4), C is (0.1,0.5,0.4), and D is (0.1,0.7,0.2). Similarly, when the mass ratio of ethylene carbonate derivative, gamma-butyrolactone, and sum of ethylene carbonate and propylene carbonate are plotted on x-z axis respectively, a tetragon with vertices (E-H) is formed in the triangular figure, where E is (0.44,0.2,0.36), F is (0.28,0.2,0.52), G is (0.08,0.4,0.52), and H is (0.08,0.56,0.36); and when mass ratio of ethylene carbonate derivative, gamma-valerolactone, and ethylene carbonate are plotted on x-z axis respectively, a tetragon with vertices (I-L) is formed in the triangular figure, where I is (0.55,0.25,0.2), J is (0.35,0.25,0.4), K is (0.1,0.7,0.2), and L is (0.35,0.55,0.1).    TECHNOLOGY FOCUS - POLYMERS - Preferred Compounds: The polymer compound contains group chosen from polyvinylidene fluoride, polyethylene oxide, polypropylene oxide, polyacrylonitrile and/or polymethacrylonitrile, in the repeating unit. EXAMPLE - Lithium hexafluorophosphate and lithium tetrafluoroborate were dissolved in mixed solvent containing 4-fluoro-1,3-dioxalan-2-one (in mass%) (65), ethylene carbonate (15) and gamma-butyrolactone (20) to form an electrolyte liquid. The electrolyte liquid was applied on anode and cathode, and heated to 50degreesC for 3 minutes to form a gel-form electrolyte layer. The electrodes with the electrolyte layer were laminated through a separator containing polyethylene film having porosity of 33% and thickness of 10 microns. The laminate was wound to form an electrode material. Battery formed using the electrode material had excellent discharge capacitance and cycle characteristics.