Inorganic-Organic Hybrid Sulfide Solid Electrolytes Based on the Tetraalkylammonium Iodide-LiI-Li₂S-P₂S₅ System

In this study, a series of novel inorganic-organic hybrid sulfide solid electrolytes was synthesized by doping Li 7 P 2 S 8 I with a selection of tetraalkylammonium iodides, including tetramethylammonium iodide (TMAI), tetraethylammonium iodide (TEAI), tetrapropylammonium iodide (TPAI), and tetrabutylammonium iodide (TBAI). The electrolytes were prepared in varying compositions, represented as (1−x) Li 7 P 2 S 8 I · x (TMAI, TEAI, TPAI, TBAI), where x values were adjusted to 0, 0.05, 0.1, and 0.2 (molar ratio) to assess their influence on the electrolyte properties. The hybrids exhibited predominantly amorphous structures. Tetraalkylammonium iodides with longer alkyl chains exhibited lower ionic conductivities. Mechanical characterization via indentation tests indicated that the incorporation of tetraalkylammonium iodides with longer alkyl chains reduced the elastic moduli of the composites. This study presents a methodological approach for modulating the structural and mechanical properties of sulfide solid electrolytes through strategic organic doping.