Anisotropic ionic conduction in composite polymer electrolytes filled with clays oriented by a strong magnetic field

To utilize the fascinating properties of clays, including their large surface areas, many dissociable cations in the interlayers and low-dimensional structure, we focused on controlling the orientation of clay layers in ion-conductive polymer electrolytes. The application of a strong magnetic field is one of the effective methods used to control the orientation of clay layers and to improve the ionic conductivity of the clay composites. In this study, two different composite films were obtained using different orientations of the magnetic field: perpendicular (M⊥) and parallel (M//) to the film surface. From two-dimensional wide-angle X-ray diffraction measurements, the montmorillonite (MMT) layers preferentially oriented along the direction of the magnetic fields in the composites. There were substantial correlations between the conductivity and the ratio of MMT layers oriented along the direction of the conductivity measurement. The lowest conductivity was observed in the M// composite, whereas the M⊥ composite showed very good conductivity. The value was higher than that of the original electrolytes (PMEO10LiClO4) at 30 °C. These results clearly suggest that the orientation direction of the MMT layers toward the direction parallel to the conductivity measurement causes an improvement in the conductivity of the composites. In particular, the conductivity value of the M⊥ composite with 5 wt% Li–MMT was 1.2 × 10−5 S cm−1 at 30 °C, which was more than six times higher than the original electrolyte.