Polyvinylidenefluoride (PVDF)-based nanocomposite polymer electrolyte (NCPE) thin films for electrochemical applications have been synthesized by solution cast technique. NCPEs have 70PVDF:30Mg(NO$_3$)$_2$ solid polymer electrolyte (SPE) with conductivity ${\sim}$7.3 9 10$^{–8}$ S cm$^{–1}$ as phase-I and various nanoparticles as phase-II, dispersed in SPE for enhancement in its conductivity. These NCPE films were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and impedance spectroscopic techniques to study the structural and electrical properties. XRD and FTIR studies of film confirms formation of complexes. From composition and temperature dependence of conductivity analysis, we have obtained an optimum conducting composition of NCPE, i.e.,70PVDF:30Mg(NO$_3$)$_2$:3ZnO with conductivity ${\sigma}$ = 3.7 9 10$^{–4}$ S cm$^{–1}$. Ionic transport number (t$_{ion}$ = 0.99) have been calculated from Wagner’s dc polarization technique. Electrochemical cell has been fabricated using cell configuration Mg|NCPE|carbon cell and various cell parameters have been calculated from their discharge characteristics.