A composite solid polymer electrolyte (CSPE) consisting of polyethyleneoxide (PEO), LiClO4 and Al2O3 of particle size 24nm was prepared by a melt-cast method. The differential scanning calorimetry (DSC) data suggested that the CSPE is in an amorphous state due to the presence of nanophase alumina. The specific conductivity versus temperature follows Vogel–Tamman–Fulscher (VTF) behavior and the activation energy has been calculated. By analogy with the Marcus theory of solvent reorganization during electron-transfer reactions, the reorganization energy of the polymer chain has been calculated from the energy of activation of ionic conduction. The ac impedance data was analyzed using a non-linear least square (NLLS) fitting program, and the resistance of the passivating film on Li and the charge-transfer resistance of the Li reaction have been evaluated. The charge-transfer resistance has been shown to follow Arrhenius behavior through the standard rate constant for the reaction. Cyclic voltammograms provided evidence of electrochemical activity at the Li/CSPE interface near ambient temperature.