This study investigates the polarization filler effects of montmorillonite on the crystal morphology and ionic conductivity of poly(ethylene oxide) solid electrolytes. Direct-current (DC) electric field was applied during the synthesis of the PEO/montmorillonite nanocomposite to induce the alignment of the montmorillonite particles between the electrodes. Differential scanning calorimetry (DSC), polarized optical micrograph (POM), X-ray diffraction (XRD) and thermogravimetry analysis (TGA) revealed that the montmorillonite particles were well dispersed and aligned in the nanocomposites through the application of the electric field. The electric field created higher ionic conductivity (ρ) as the anisotropic clay mineral particles provided an ion conducting channel parallel to the electric field in the PEO matrix of low crystallinity.