Exceptionally high sodium ion conductivity and enhanced air stability in Na3SbS4 via germanium doping

Abstract

In addition to the widely used lithium-ion secondary batteries, more and more concerns have been paid to solid-state batteries (SSBs) in the research on future-generation energy storage systems. The availability of sodium solid electrolytes, especially those with excellent ambient temperature conductivity and prominent chemical stability, is crucial for sodium-based SSBs. In this study, Na3.1Ge0.1Sb0.9S4, a novel sodium-ion solid-state electrolyte, was obtained via a solid-state chemical reaction utilizing the economical Na2S·9H2O as one of the raw ingredients. The properties of this new electrolyte were examined by using X-ray diffractometry, Raman spectroscopy, differential scanning calorimetry, scanning electron microscopy, and electrochemical techniques. The Na3.1Ge0.1Sb0.9S4 electrolyte, which released low amounts of H2S under ambient conditions, demonstrated the ionic conductivity of 5.1 × 10−3 S/cm at normal atmospheric temperature and the conducting activation energy of 0.156 eV. The enhanced ionic conductivity was attributed to the improvement of crystallinity and the unit cell enlargement caused by interstitial sodium defects.