Exploration of synthesis and Li reactivity of layered Ag-based oxychalcogenides

Abstract

Tetragonal layered “1111-type” oxychalcogenides can exhibit rich intercalation chemistry very much like the layered electrode materials in Li-ion batteries such as LiCoO2 or graphite. This opens up a possibility to design new high energy density positive electrode materials that combine key advantages of anionic redox such as high voltage operation and low hysteresis observed in layered Li-rich oxides and Li-rich sulfides, respectively, that motivated our earlier study on Cu-based oxychalcogenides. As a natural step forward, in this work we explore the layered Ag-oxychalcogenides AgLaOS and AgBiOX (X= S/Se) with a particular focus on the topotactic reduction reactions occurring both during their synthesis and during their reaction with lithium. We synthesized AgLaOS and AgBiOX by adding Ag to LaOS* and BiOX*. We show that lithiation of AgLaOS progresses via Li-Ag displacement-alloying, while lithium addition to the Bi-based oxychalcogenides results in displacement-conversion-alloying for AgBiOS compared to multiphasic reaction-conversion-alloying in case of AgBiOSe. We further compare the lithium reactivity of these Ag-based compounds to related oxychalcogenides with or without Cu, rationalizing the differences with theoretical calculations. Overall, through this work we project the diverse topochemical reactivity of layered Ag-based oxychalcogenides.