AC conductivity studies of polyethylene oxide-garnet-type Li₇La₃Zr₂O₁₂ hybrid composite solid polymer electrolyte films

We have investigated both AC dielectric permittivity and ionic conductivity of hybrid composite solid polymer electrolyte (CSPE) films (~100 mm) comprised of sub-micron sized aluminum substituted cubic Li₇La₃Zr₂O₁₂ (LLZO) particles dispersed in polyethylene oxide-LiClO₄ (PEO-LiClO₄) matrix with [EO]:[Li] = 15:1. The complex AC permittivity and conductivity were determined using the measured electrical impedance spectra in the range of 1 Hz to 300 kHz and analyzed using generalized power-law that accounts for the effect of electrode polarization. The ionic and segmental relaxation times obtained from fitting the experimental data indicate a strong coupling between the ionic motion and segmental dynamics. Further, the observed temperature dependent conductivity follows the Vogel-Tammann-Fulcher (VTF) behavior implying a close correlation between ionic conductivity and segmental relaxation in these polymer electrolytes. The VTF model yields an activation energy of 0.32 eV for PEO-LiClO₄ film, and 0.07 eV for PEO-LLZO-LiClO₄ composite film, consistent with the observed enhancement in conductivity by two orders of magnitude at 30 ^oC upon the addition of LLZO particles. Details preparation of CSPE films and the analyses will be presented.