Gel polymer electrolytes composed of poly(vinylidene fluoride-hexafluoropropylene) copolymer, poly(vinylidene fluoride) polymer, PC+DEC as plasticizer and LiClO4 as salt have been synthesized by solvent casting technique with varying the plasticizer-salt concentration ratio systematically. Complex impedance spectroscopy has been carried out to investigate ionic conduction in P(VDF-HFP)–(PC+DEC)–LiClO4 and PVDF–(PC+DEC)–LiClO4 electrolyte systems. Transport number measurements have been made by Wagner’s polarization technique. With all other parameters same, P(VDF-HFP) electrolytes exhibit higher ionic conductivity and transport number as compared to PVDF based electrolytes which could be attributed to higher degree of amorphicity in the P(VDF-HFP) system. XRD and FTIR studies have been conducted to investigate the structural and complexation in the polymer gel electrolytes. Microstructural studies by SEM exhibit higher amorphicity and solvent retention capability for P(VDF-HFP)–(PC+DEC)–LiClO4 system than those of PVDF–(PC+DEC)–LiClO4 system.