Composite electrolytes Cs3(H2PO4)(HSO4)2/SiO2 with high proton conductivity

Conductivity measurements of mixed cesium hydrogen disulphate phosphate were carried out. Additional thermodynamic data on pure Cs3(HSO4)2H2PO4 were obtained.New highly conductive (50–200 °C) composite proton electrolytes based on Cs3(HSO4)2H2PO4 and silica were synthesized. The properties of (1 − x)Cs3(HSO4)2H2PO4/xSiO2 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 Cs3(HSO4)2H2PO4 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 Cs3(HSO4)2H2PO4/SiO2 composites depends on composition, reaching a maximum at ∼ 15–35 vol.% silica and then decreasing due to a percolation effect. A disordered state of Cs3(HSO4)2H2PO4 with increased proton conductivity was realized for highly dispersed silica. The conductivity of the Cs3(HSO4)2H2PO4/SiO2 composite was shown to exceed that of the CsHSO4/SiO2 systems by one order of magnitude.