Electrochemical properties of superionic conductors CsAg₄Br_3-хI_2+х

Abstract

CsAg4Br3–хI2+х solid solutions with x=0.38; 0.50; 0.63 were prepared by solid-phase synthesis; the single-phase of the products was confirmed by X-ray diffraction and differential scanning calorimetry. Studies of the electrical transport characteristics of CsAg4Br3–хI2+х included measurements of the ionic conductivity by the four-probe method in the range of –50…+120°C and an evaluation of the electronic component of the conductivity by the Hebb-Wagner method. It was shown that the ionic conductivity of CsAg4Br3–хI2+х solid solutions in the studied range of compositions is practically independent of x and is very close to that of the well-known superionic conductor RbAg4I5. The activation energy of conduction for all studied compounds is about 10 kJ mol–1. The oxidation potential determined by the stepwise polarization technique for CsAg4Br3–хI2+х solid solutions is noticeably higher than that of RbAg4I5, and is in the range of 0.75–0.78 V (vs. Ag0/Ag+). The high electrochemical characteristics of CsAg4Br3–хI2+х (0.38≤x≤0.63) and the absence of polymorphic transitions in the studied range from –160°C to the melting point (175 – 178°С) make these materials promising for use in electrochemical devices based on solid electrolytes, especially for low temperature applications.