Pottery glaze-derived sintering aids for the synthesis of NASICON electrolytes with high ionic conductivity and relative density

Abstract

Generally, the densification of NASICON-type structured ceramics requires high sintering temperatures and prolonged sintering durations. In this study, glass frit, a glaze component used in pottery production, was successfully utilized as a sintering aid to obtain dense NASICON electrolytes at relatively low sintering temperatures and short sintering times. When glass frit was added to the synthetic process, it induced liquid-phase sintering without any detrimental effects on the crystalline structure of NASICON. The NASICON prepared with the optimized ratio of glass frit exhibits not only a high ionic conductivity of 2.36 × 10⁻³ S cm⁻¹, which is almost 5.7 times higher compared to that of the NASICON prepared without glass frit but also a significantly enhanced relative density from 79.8% to 98.5%. Additionally, the utilization of the glass frit resulted in a threefold increase in the critical current density, rising from 0.15 mA cm⁻² to 0.45 mA cm⁻². The solid-state sodium battery, composed of a Na₃V₂(PO₄)₃ cathode (NVP) and a sodium metal anode, exhibits an initial discharge capacity of 101.2 mA h g,_NVP⁻¹ at 0.1 A g⁻¹ and maintains 86% of its capacity after 100 cycles at room temperature. This study holds significant importance as it demonstrates the practical applicability of a readily accessible material as a sintering aid for advanced electrolytes.