Na+-ion conducting glasses

Na⁺-ion conduction in glass is discussed with the aim of selecting suitable electrolytes for use in Na/S cells operating around 350°C. From an extensive survey of many glass systems including silicates, borates, etc., it is found that the conductivity increases with increasing optical basicity (Λ), while the activation energy falls toward an apparent limiting value of ca. 50 kJ mol^?1. The use of special additives such as NaCl does not lead to any further improvement. Several “optimised ionic conductors” have been identified, where σ ? 10^?2 S cm^?1 at T_g. These are the best materials for use in battery applications provided they are stable in the cell environment.