Effect of SiO2 morphology and pores size on the proton nanocomposite electrolytes properties

Abstract

The composite solid electrolytes (1−x)MeHSO4–xSiO2, (where Me=Cs, Rb, x=0–0.8) have been studied by complex impedance, DSC and X-ray diffraction methods. The used SiO2 varied in specific surface areas (13–580 m2g−1), pores size (R=14–1000 Å) and pores size distribution. The low-temperature conductivity of the composites was shown to exceed by 1–3 orders of magnitude that of the individual salts. It depended on SiO2 content, silica pores size and their distribution. There is optimum silica pores size in a range of 35–100 Å, where the most composite conductivity increase takes place; the ionic component becomes either partially or completely amorphous with x increasing (“dimensional effect”). The MeHSO4 dispergation mainly proceeds in composites with R=170 Å. The MeHSO4 state does not change when the SiO2 pores size is 1000 Å. In systems with R=14 Å both MeHSO4 low-temperature phase and amorphous state are observed.