TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The alcohol derivative comprises ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, diethylene glycol, alkanediol, ethoxylated alkanediol(ethoxylated alkanediol), propoxylated alkanediol(propoxylated alkanediol), trimethylolpropane, ethoxylated trimethylolpropane, propoxylated trimethylolpropane, ditrimethylol propane, ethoxylated ditrimethylol propane, propoxylated ditrimethylol propane, pentaerythritol, ethoxylated pentaerythritol, propoxylated pentaerythritol, dipentaerythritol, ethoxylated dipentaerythritol, propoxylated dipentaerythritol, bisphenol A, ethoxylated bisphenol A, or propoxylated bisphenol A. The alkyl acrylate comprises 4-8 carbon alkyl acrylate. The polyester polyol-based monomer has a weight average molecular weight of 16000-20000. The polyester polyol-based monomer has a number average molecular weight of 6000-8000. The additive comprises: 20-80 wt.% of the polyester polyol-based monomer; 10-60 wt.% of the alkyl acrylate; and 1-40 wt.% of the phosphate-based compound. The additive comprising the polyester polyol-based monomer, alkyl acrylate, and phosphate-based compound is present in a weight ratio of 75:15:10-60:20:20. The additive is included at 1-10 pts. wt. based on 100 pts. wt. of the non-aqueous organic solvent. EXAMPLE - 7 wt.% Of an additive (obtained by mixing a polyester polyol-based monomer of formula (A2-(X2-O-C(=O)-(CH2)x1-C(=O)-O)(-Y2-O-C(=O)-(CH2)y1-C(=O)-O)(-Z2-O-C(=O)-(CH2)z1-C(=O)-O)-B2) (where A2, B2 is (CH2=C(CH3)-C(=O)-O-(CH2)2-NH-C(=O)-), X2 is residual group derived from ethyleneglycol, Y2 is residual group derived from diethylene glycol, Z2 is residual group derived from trimethylolpropane, and x1, y1 and z1 is 4), hexyl acrylate, and phosphoric acid triallyl ester in a weight ratio of 69:25:6) and 93 wt.% of a mixed solution (prepared by mixing ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate in a volume ratio of 3:2:5) were mixed to prepare non-aqueous organic solvent. Then 1.3 M of lithium hexafluorophosphate was dissolved in it to obtain a pre-gel. 350 ppm Of 2,2'-azobis(isobutyronitrile) azo-based polymerization initiator was added to the pre-gel based on the weight of the pre-gel and dissolved in it to obtain the polymer electrolyte composition.