TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Polymer: The polymeric structure formed by physical process crosslinking is selected from acrylonitrile homopolymer, an acrylonitrile-vinyl acetate copolymer, acrylonitrile-acrylic acid copolymer, acrylonitrile-methacrylic acid copolymer, polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyether and ethylene oxide copolymer. Preferred Covalent Bond: The cross-linked covalent bond is selected from vinyl group, epoxy group, ether group, amide group and urethane group. Preferred Method: The polymeric structure which has crosslinked covalent bond is formed by irradiating ultraviolet rays into the mixture. The crosslinked polymeric structure by physical process, is formed by ultraviolet irradiation or heat. The polyelectrolyte is coated or impregnated to anode board and cathode plate, and cross-linked thermosetting resin is formed by heating and cooling the mixture followed by pressing against anode and cathode. EXAMPLE - Trimethylol propane triacrylate (in weight parts) (8) crosslinking agent, acrylic acid oligomer (20) and benzyl dimethyl ketal (2) polymerization initiator were mixed. Acrylonitrile-vinyl acetate (AN-VAc) copolymer (50) with molecular weight of 500000, ethylene carbonate (EC) (140), propylene carbonate (PC) (60) and lithium phosphorus hexafluoride (LiPF6) electrolyte salt (30) were mixed with the reaction mixture and vacuum degassed to form solution. The solution was coated on polyethylene terephthalate film followed by irradiatieon of ultraviolet rays in presence of an argon gas to obtain crosslinked covalent bond which is maintained at -20degreesC for 1 day. A tangle was made to form on film after heating the film for 30 minutes at 90degreesC. AN-VAc copolymer was fused to obtain a polyelectrolyte of 14x24 mm. The electrolyte (EC/PC/LiPF6 = 4,2/1) was impregnated between an anode and cathode. The polyelectrolyte was transferred and inserted to obtain a cell. The cell was introduced to resin film bag followed by vacuum sealing and air-tight was performed to obtain a battery which was found to have excellent cycle property and heat resistant, and discharge property of 93 and capacitive maintenance factor of 95%.