Composite electrolytes Cs 3(H 2PO 4)(HSO 4) 2/SiO 2 with high proton conductivity

Abstract

Conductivity measurements of mixed cesium hydrogen disulphate phosphate were carried out. Additional thermodynamic data on pure Cs 3(HSO 4) 2H 2PO 4 were obtained. New highly conductive (50–200 °C) composite proton electrolytes based on Cs 3(HSO 4) 2H 2PO 4 and silica were synthesized. The properties of (1 − x)Cs 3(HSO 4) 2H 2PO 4/ xSiO 2 composites ( x = 0–0.95) were studied by differential scanning calorimetry, X-ray powder diffraction and complex impedance methods. Heterogeneous doping was shown to increase the low temperature phase conductivity of Cs 3(HSO 4) 2H 2PO 4 by more than one order of magnitude. The observed jump in conductivity becomes diffuse, shifts to lower temperatures and disappears at x = 0.7. The conductivity of Cs 3(HSO 4) 2H 2PO 4/SiO 2 composites depends on composition, reaching a maximum at ∼ 15–35 vol.% silica and then decreasing due to a percolation effect. A disordered state of Cs 3(HSO 4) 2H 2PO 4 with increased proton conductivity was realized for highly dispersed silica. The conductivity of the Cs 3(HSO 4) 2H 2PO 4/SiO 2 composite was shown to exceed that of the CsHSO 4/SiO 2 systems by one order of magnitude.