Aqueous synthesis of Na3-2xSb1-xWxS4-xIx solid-state electrolytes with ultrahigh ionic conductivity

Chalcogenide solid-state electrolytes (SSEs) offer advantages of high safety, excellent energy density and low cost for all-solid-state sodium ion batteries. However, the large-scale preparation and applications of SSEs are still limited by both their demanding fabrication conditions and the lack of a deep understanding of chemical degradation mechanism. Here, we develop a stable high-performance SSEs, namely Na2.8Sb0.9W0.1S3.9I0.1 SSEs, through a facial aqueous solution synthesis method. This SSE exhibits an ultra-high room-temperature ionic conductivity of 10.3 mS cm ^-1 , attributed to the widened ion migration channels after W and I substitution, introduction of sodium vacancies and 3D conduction pathways. Oxygen (instead of water) is found to critically affect the chemical stability of Na2.8Sb0.9W0.1S3.9I0.1 SSEs. Moreover, the SSE-based all-solid-state batteries (ASSBs) demonstrate excellent cycling performance in a full Na3Sn|SSEs|TiS2 battery with capacity retention of 127 mAh g ^-1 after 1000 cycles at 0.1 A g ^-1 . This aqueous synthesis strategy provides a pathway towards large-scale fabrication of both chemically stable chalcogenide sodium-ion conductors and cost-effective superior all-solid-state sodium-ion batteries.