Improved Air Stability of Sulfide Electrolytes for All-Solid-State Li Batteries

Sulfide-based solid electrolytes (SEs) are receiving increasing attention due to their high ionic conductivities (up to 10 -2 S cm -1 at room temperature) that can be comparable to the liquid electrolytes. 1 However, the air stability of sulfide SEs is very poor. 2, 3 Most developed sulfide SEs are prone to turn bad when exposed to the moisture. The generated H 2 S is dangerous, which places the commercialization of sulfide SEs into a challenging situation. 2, 3 In our work, to improve the air stability of sulfide SEs, we employed element substitution (Sn and Sb) for the problematic element (P) in conventional sulfide SEs (Li 3 PS 4 , Li 6 PS 5 I, Li 10 GeP 2 S 12 ) based on the hard and soft acid and base theory (HSAB). 4, 5, 6 Our results suggest that Sn and Sb-substituted sulfide SEs show significantly improved air stability compared with the pristine sulfides. Meanwhile, it is found that the Sn or Sb element substitution effectively enhance the ionic conductivity as well as Li metal compatibility in some cases. Various structural (e.g., X-ray diffraction, X-ray absorption near edge spectroscopy, solid-state nuclear magnetic resonance) and electrochemical characterizations are employed to identify the mechanism of the improvements are related to the Sn/Sb substitution-derived crystal structure, reinforced bonding energy, and the optimized electrode/electrolyte interfaces. Our studies provide a new idea of designing functional sulfide composition to realize improved air stability coupling with other essential properties. Re ferences N. Kamaya, R. Kanno*, et al. A lithium superionic conductor, Nat. Mater . 2011, 10 , 682-686. C. Yu, F. Zhao, J. Luo, X. Sun*. Recent Development of lithium argyrodite solid-state electrolytes for solid-state batteries: synthesis, structure, stability and dynamics. Nano Energy 2021, 83 , 105858. F. Zhao, S. Zhang, Y. Li*, X. Sun*. Emerging characterization techniques to understand electrode interfaces in all-solid-state lithium batteries. Small Struct. 2021, DOI: 10.1002/sstr.202100146. F. Zhao, J. Liang, X. Sun*, et al. A Versatile Sn-Substituted Argyrodite Sulfide Electrolyte for All-Solid-State Li Metal Batteries, Adv. Energy Mater. 2020, 10 , 1903422. F. Zhao, X. Sun*, et al. An Air-Stable and Li-Metal-Compatible Glass-Ceramic Electrolyte enabling High-Performance All-Solid-State Li-Metal Batteries. Adv. Mater. 2021, 33 , 2006577. J. Liang, X. Sun*, et al. Li 10 Ge(P 1–x Sb x ) 2 S 12 Lithium-Ion Conductors with Enhanced Atmospheric Stability, Chem. Mater. 2020, 32 , 2664-2672.