Preparation and degradation of high air stability sulfide solid electrolyte 75Li2S·25P2S5 glass-ceramic

Abstract

The development of next-generation lithium-ion batteries relies heavily on the design and manufacture of solid electrolytes with excellent ionic conductivity and air stability. 75Li2S·25P2S5 glass-ceramic is a desirable and promising solid-electrolyte material, but further research is needed to understand how certain synthesis factors affect the local structure and ionic conductivity of the material. In addition, the majority of the existing research on the air stability of solid electrolytes simply record the change in the amount of H2S released over time, which is insufficient. Herein, we highlight the impact of a range of conditions in the ball milling stage (including jar filling factor, rotation speed, ball-to-powder ratio and total milling time) and the calcination stage (including heat-treatment temperatures and heat-treatment durations) on the 75Li2S·25P2S5 glass-ceramic synthesis, through powder X-ray diffraction, Raman and electrochemical impedance spectroscopy. We have found that this material has a relatively high air stability under optimal synthesis situations, taking approximately 6.5 min to release 5 ppm H2S. In addition, we present degradation studies on 75Li2S·25P2S5 glass-ceramic by electrochemical impedance spectroscopy, scanning electron microscope, energy dispersive spectroscopy and Raman. After being exposed to air for a period of time, the ionic conductivity of 75Li2S·25P2S5 glass-ceramic significantly decreased, and its morphology and structure were severely deteriorated. It is most likely that the sample eventually generates a mixture of Li3PO4, Li2SO4 and S8.