TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Component: The polymerization initiator is hydrogen peroxide.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Component: The polymerization initiator is benzoyl peroxide, acetyl peroxide, dilauryl peroxide, di-tert-butyl peroxide, t-butyl-peroxy-2-ethylhexanoate, cumyl hydroperoxide, t-amyl-(2-ethylhexyl)monoperoxy carbonate, 2,2'-azobis (2-cyanobutane), 2,2'-azobis (methylbutyronitrile), azobisisobutyronitrile, or 2,2'-azobisdimethyl-valeronitrile. The polymer electrolyte monomer is a monomer having a polymerizable functional group comprising a vinyl group, an epoxy group, an allyl group, or a (meth)acryl group. The electrolyte solvent is cyclic carbonate, linear carbonate, lactone, ether, ester, sulfoxide, acetonitrile, lactam, ketone, or their halogen derivatives. The electrolyte salt is a combination of a positive ion comprising lithium sodium, or potassium; and a negative ion comprising hexafluorophosphate, tetrafluoroborate, chloride, bromide, iodide, hexafluoroarsinate, acetate, trifluoromethanesulfonate, bis(trifluoromethane sulfonyl)imide, or tris(trifluoromethanesulfonyl)methide. The monomer is included in an amount of 0.01-10 pts. wt., and the polymerization initiator is included in an amount of 0.01-5 pts.wt. based on 100 parts by weight of a mixture of the electrolyte solvent and the electrolyte salt.    TECHNOLOGY FOCUS - POLYMERS - Preferred Component: The non-woven fabric separator is formed of polyethylene or polypropylene. EXAMPLE - A solution, in which 0.00825 g t-butyl peroxy-2-ethylhexanoate as a polymerization initiator was dissolved in acetone, was uniformly coated on a polyolefin-based non-woven fabric separator, and dried to obtain a separator coated with the polymerization initiator. About 1M lithium hexafluorophosphate was dissolved in a non-aqueous electrolyte solvent having a composition ratio of ethylene carbonate to ethylmethylcarbonate of 1:2 to prepare a liquid electrolyte. Trimethylolpropane triacrylate (5 pts.wt.) as a polymer electrolyte monomer was added to prepare 3.3 g gel polymer electrolyte composition. About 94 wt.% lithium cobalt oxide as a cathode active material, 3 wt.% carbon black as a conductive material, and 3 wt.% polyvinylidene fluoride (PVdF) as a binder were added to N-methyl-2-pyrrolidone (NMP) as a solvent to prepare a cathode slurry. The cathode slurry was coated on an aluminum thin foil of a cathode current collector having a thickness of 20 mu m, dried, and roll-pressed to obtain a cathode. About 96 wt.% carbon powder as an anode active material, 3 wt.% PVdF as a binder, and 1 wt.% carbon black as a conductive material were added to NMP as a solvent to prepare anode slurry. The anode slurry was coated on a copper thin foil of an anode current collector having a thickness of 10 mu m, dried, and roll-pressed to obtain an anode. The separator coated with the polymerization initiator and the gel polymer electrolyte composition was provided. The separator was interposed between the cathode and the anode, and the battery elements were rolled in a jelly roll fashion, and placed in a battery case. The gel polymer electrolyte composition was introduced into the battery case to obtain a secondary battery.