Preparation of Na/S cell using silicophosphate in the Na₂O-Y₂O₃-P₂O₅-SiO₂ system and measurement of the transport number of sodium ion by the electromotive force method

Abstract

Sodium superionic conductor in the Na₂O-Y₂O₃-P₂O₅-SiO₂ system was synthesized by sol-gel method. The obtained samples with a composition of Na_5.2Y_0.8P_0.4Si_3.6O_12.0 showed high conductivity at 310°C of σ₃₁₀=9.3×10^-2Scm^-1. Using this solid electrolyte, Na/S cell was prepared. Open-circuit voltage of the cell was 1.94V at 310°C and the transport number was calculated at 0.990. The results of measurement of durability and discharge behavior for the cell suggested that minuteness and homogeneity were very important to evaluate solid electrolyte of Na/S cell was well as conductivity.