Magnesium ion‐conducting gel polymer electrolyte nanocomposites: Effect of active and passive nanofillers

Abstract

A novel magnesium (Mg) ion conducting nanocomposite gel polymer electrolyte (GPE) films comprising a solution of Mg‐salt, Mg trifluoromethanesulfonate [Mg‐triflate or Mg(Tf)2] in a mixture of ethylene carbonate (EC) and propylene carbonate (PC), entrapped in a host polymer poly(vinylidenefluoride‐hexafluoropropylene) (PVdF‐HFP) has been reported. The effect of dispersion of nanosized passive filler aluminum oxide (Al2O3) and active filler Mg aluminate (MgAl2O4) in the films was studied. Free standing transparent nanocomposite films are obtained with excellent dimensional stability. The filler‐polymer interactions and possible conformational changes in the host polymer PVdF‐HFP due to the liquid electrolyte entrapmentment and dispersion of nanosized Al2O3 and MgAl2O4 fillers are examined by X‐ray diffraction, field emission scanning electron microscopy, and tensile strength measurement. A nanocomposite films with 30 wt% Al2O3 and 20 wt% MgAl2O4 fillers offer maximum ionic conductivity of 3.3 × 10−3 and 4.0 × 10−3 S cm−1, respectively, at room temperature. The temperature dependence of electrical conductivity of undispersed and nanocomposites GPE follows the Vogel‐Tammen‐Fulcher behavior. The Mg ion conduction in the nanocomposites GPE films is confirmed from electrochemical impedance spectroscopy, cyclic voltammetry, and transport number measurement. The Mg2+ ion transport number has been found to be significantly enhanced up to 0.66 for the dispersion of 20 wt% MgAl2O4 nanofiller, indicating a substantial enhancement in Mg2+ ion conductivity. The nanocomposites films possess a good electrochemical stability window, which indicates their potential applicability as electrolytes in ionic devices including Mg batteries. POLYM. COMPOS., 40:1295–1306, 2019. © 2018 Society of Plastics Engineers