Effect of Li-ion concentration on ionic conductivity of polyethylene oxide-cubic-Li₇La₃Zr₂O₁₂ hybrid composite solid polymer electrolyte films

We have investigated the effect of Li-ion concentration on ionic conductivity of polyethylene oxide-LiClO₄ (PEO-LiClO₄) films as well as 50 wt% cubic-Li₇La₃Zr₂O₁₂ (LLZO) filled PEO-LiClO₄ hybrid composite solid polymer electrolyte (CSPE) films with EO:Li ratio of 15, 12 and 10. The complex AC permittivity and conductivity were determined using the measured electrical impedance spectra in the range of 1 Hz to 300 kHz. The data was fitted to a generalized power-law for complex conductivity that accounts for the effects of electrode polarization. The observed temperature dependent conductivity follows the Vogel-Tammann-Fulcher (VTF) behavior implying a close correlation between ionic conductivity and polymer segmental relaxation. In addition to increased mechanical robustness and thermal stability, the CSPE films show higher values of conductivity ~ 1- 2×10^-4 S/cm at lower Li-ion concentrations (EO:Li ratio of 15 and 12) compared to those of PEO-LiClO₄ (~ 10^-6 -10^-5 S/cm). The analyses of data with VTF model yields the lowest activation energy of ~ 0.05 eV for PEO-LiClO₄-LLZO film with EO:Li = 12. Details of preparation of films and the analyses will be presented.