For the next generation lithium batteries, polymer-based electrolytes are promising candidates resolving issues from liquid electrolyte such as leakage, flammability, and explosion. Various attempts have been carried out to develop polymer electrolyte based on poly(ethylene oxide) (PEO), polyacrylonitrile, polyvinylidene fluoride, etc., resulting in suppression for dendrite growth on Li metal and mechanical support against internal or external shock as well. Among these polymer electrolytes, PEO has been widely used due to their relatively high ionic conduction through hopping of Li ions. Herein, we synthesized poly(GAP-co-THF) diol (PGT) having similar main chain to PEO while containing azide groups in side chain. To enhance processability of polymer electrolytes, thermal crosslinking process was performed via azide-alkene cycloaddition between PGT and poly(ethylene glycol) diacrylate with lithium bis(trifluoromethanesulfonyl)imide without any initiators and organic solvents. Thickness controllable thin film of polymer electrolyte was obtained after crosslinking process, resulting in outstanding advantages with respect to stacking of batteries. To check electrochemical stabilities and cell performances of these polymer electrolytes, cyclic voltammetry, linear symmetric voltammetry, LiFePO4(LFP)∥Li cell, and Li symmetric cell test were accomplished.