Electrical and electrochemical properties of magnesium ion conducting composite gel polymer electrolytes

摘要

The effect of micro-and nano-sized MgO and nano-sized SiO_2 dispersion on the electrical and electrochemical properties of poly(vinylidene fluoride-hexafluoropropylene) (PVdF-HFP) based Mg~(2+) ion conducting gel polymer electrolyte has been investigated. The gel electrolytes have been characterized using electrical conductivity, cationic transport number (t _+) measurements and cyclic voltammetry. A two-maxima feature has been observed in the 'conductivity versus composition' curve at ～3 wt% and 10-15 wt% of the filler contents. The highest conductivity has been obtained for the SiO_2 dispersed gel electrolyte of ～1 × 10~(-2) S cm~(-1) for 3 wt% and ～9 × 10~(-3) S cm~(-1) at 15 wt% content. The value of 't_+' is found to be enhanced substantially with increasing amount of MgO (both micro-and nanoparticles), whereas in the case of SiO_2 dispersion the value does not increase substantially. The highest 't_+' value of ～0.44 has been obtained 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, which supports Mg~(2+) ion motion. A substantial increase in the amount of anodic and cathodic peak currents is observed due to the addition of nano-sized MgO particles in the gel polymer electrolyte, whereas in the cases of micrometre-sized MgO and nano-sized SiO_2 the enhancement is not significant. The enhancement in conductivity in SiO_2 dispersed nanocomposite gel electrolyte is predominantly due to anionic motion.