Lithium superionic solid electrolyte: Phosphorus-free sulfide glass of LiSbGe(4-x)/4S4-xClx

Abstract

This study demonstrates a novel glass compound of LiSbGe(4-x)/4S4-xClx (x = 0 −0.7) and validate its efficacy as a solid electrolyte for all-solid-state-batteries. Phosphorous-free sulfide solid electrolytes of LiSbGe(4-x)/4S4-xClx (x = 0 −0.7) are first designed and synthesized based on the hard and soft acid-base (HSAB) theory by alternating lithium thio-phosphate compounds. The LiSbGeS4 has exceptional amorphous nature in a broad temperature range over 600 ℃. As the LiSbGeS4 does not contain phosphorus, it has improved chemical stability and wide operating potential window in the range of 0.30−2.00 V vs. In/InLi. Among the series of LiSbGe(4-x)/4S4-xClx (x = 0 −0.7), the mostly optimized LiSbGe0.875S3.5Cl0.5 (x = 0.5) exhibits a superionic conductivity of 1.82 × 10−3 S·cm−1, a small activation energy of 0.18 eV, and a broad operating potential window of 0.60−2.00 V vs. In/InLi. The LiSbGe0.875S3.5Cl0.5 (x = 0.5) is remarkably stable at high current densities above 48.5 mA·cm−2 and shows reversible cyclability with no short circuit above 710 h (328 cycles). The exceptionally increased solid electrolyte performance of LiSbGe0.875S3.5Cl0.5 (x = 0.5) is rationalized by the weakened bond strength with Li+ and enhanced amorphous nature of the anionic skeleton of LiSbGe0.875S3.5Cl0.5 (x = 0.5) through LiCl-doping and press-induced sintering, respectively. The results of this study contribute towards the development of phosphorus-free solid electrolytes with promising electrochemical attributes and also towards understanding the Li-ion conduction mechanism in aliovalent-substituted glass electrolytes. © 2025 Elsevier Ltd