"Oxygen Into Sulfur"- New Synthesis of Sulfide Solid Electrolyte by Oxygenophilic Boron

Sulfide solid electrolytes (SEs) with high ionic conductivity and facile formability provide great promise to construct high energy density and safe all-solid-state batteries (ASSBs). However, the poor air stability of sulfide feedstock and SEs makes the synthesis, storage, and postprocessing of the materials in a dry inert-gas atmosphere, which increases the complexity and cost of the production process. Here, a boron-assisted sulfurization synthesis method is reported for preparing various sulfide SEs from oxide raw materials, including Li₄SnS₄, Na₃SbS₄, and Li₆PS₅X (X = Cl, Br). Boron bonds oxygen from oxide precursors and can be separated, while elemental sulfur reacts with the remaining mixture to form sulfide SEs. Furthermore, nontoxic boron and sulfur ensure the safety of production. Finally, the assembled lithium symmetric batteries and all-solid-state batteries with prepared sulfide SEs exhibit stable cycling. Hence, this work may be important for the practical production and application of sulfide-based ASSBs.