Magnesium ion-conducting gel polymer electrolytes dispersed with nanosized magnesium oxide

摘要

Experimental investigations are performed on novel magnesium ion-conducting gel polymer electrolyte nanocomposites based on poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP), dispersed with nanosized magnesium oxide (MgO) particles. The nanocomposite materials are in the form of freestanding films. Various physical and electrochemical analyses demonstrate promising characteristics of these films, suitable as electrolytes in rechargeable magnesium batteries. The optimized material with 3 wt.% MgO offers a maximum electrical conductivity of ～8 × 10~(-3) S cm~(-1) at room temperature (～25 ℃) with good thermal and electrochemical stabilities. The ion/filler-polymer interactions and possible con-formational changes in host polymer PVdF-HFP due to the liquid electrolyte entrapment and dispersion of nanosized MgO are examined by Fourier transform infrared (FTIR), X-ray diffraction (XRD) and scanning electron microscopic (SEM) methods. The Mg~(2+) ion conduction in the gel film is confirmed from the cyclic voltammetry, impedance spectroscopy and transport number measurements. The Mg~(2+) ion transport number (t_+) is enhanced substantially and found to have a maximum of ～0.44 for the addition of 10 wt.% MgO nanoparticles. The enhancement in t_+ is explained on the basis of the formation of space-charge regions due to the presence of MgO:Mg~(2+)-like species, that supports Mg~(2+) ion motion.