Search for new silver-ion solid electrolytes for use in batteries

Abstract

THE α-phase of AgI, which is stable above 146 °C, has a silver-ion conductivity of 1 Ω⁻¹ cm⁻¹ at 150 °C (ref. 1), which would make it a suitable solid electrolyte for high temperature batteries. The room-temperature conductivity of the stable phase of AgI is disappointingly low (10⁻⁶−6 Ω⁻¹ cm⁻¹) and although samples with conductivities approaching 3 × 10⁻⁴ Ω⁻¹ cm⁻¹ can be prepared², such values are insufficient to make it of use as an electrolyte in solid state batteries at room temperature. There is, however, considerable interest in producing solid electrolytes, based on AgI combined with organic cation iodides to give high silver-ion conductivity at room temperature^4–9. We report here on the conductivities of representatives of three hitherto unexamined classes of compounds, AgI–selenonium iodide, AgI–telluronium iodide and AgI–bis-sulphonium diiodide.