Montmorillonite Composite Polymer Electrolytes Displayed Exceedingly High Ion Conductivity Oriented By Electric Field

Abstract

Solid polymer electrolytes are nonvolatile with strong film forming strength. It is considered as critical components for next generation lithium battery to meet the many demnds of growing mobile electronic power industry. Improving ionic conductivity of polymer electrolyte suitable for LIB, is the most urgent technical challenge. We report in this study a novel polymer electrolyte system by incorporating surface functionalized clay into the PVDF-HFP/Ionic liquid/Li salt system under applied an electric field. Mineral clays bear large surface areas, high aspect ratio, numerous dissociable cations in the interlayer and low-dimensional nano structure. The application of electric field has effectively oriented clay layers uniformly and dispersed it homogeneously to form an ordered and alignment nanostructure which is confirmed by SEM. This super ionic feature is extremely favorable for delivering high ion conductivity in the solvent free electrolytes where the long range ordered inorganic moiety served to corporate rapid ion transport. X-ray diffraction and DSC measurements indicated that the α-phase PVDF crystalline form was decreased by the electric field. The variety of crystalline degree of the polymer matrix was determined. The ionic conductivity of the composite electrolyte were measured to over 10-3 S cm-1. AC impedance spectroscopy revealed that the ionic conductivity of the electrolyte membrane containing 3 wt% MMT attains an order of 10−3 S cm−1 at room temperature. Coin cells assembled with the LFP cathode reversible discharge capacities of 140 mAh g−1 at 0.1C, accompanied with high coulombic efficiency over 40 cycles. Figure 1