Design of metastable oxychalcogenide phases by topochemical (de)intercalation of sulfur in La2O2S2

Recent advances and perspectives on intercalation layered compounds part 1: design and applications in the field of energy

Herein, initially, we present a general overview of the global financial support for chemistry devoted to materials science, specifically intercalation layered compounds (ILCs). Subsequently, the strategies to synthesise these host structures and the corresponding guest-host hybrid assemblies are exemplified on the basis of some families of materials, including pillared clays (PILCs), porous clay heterostructures (PCHs), zirconium phosphate (ZrP), layered double hydroxides (LDHs), graphite intercalation compounds (GICs), graphene-based materials, and MXenes. Additionally, a non-exhaustive survey on their possible application in the field of energy through electrochemical storage, mostly as electrode materials but also as electrolyte additives, is presented, including lithium technologies based on lithium ion batteries (LIBs), and beyond LiBs with a focus on possible alternatives such XIBs (X = Na (NIB), K (KIB), Al (AIB), Zn (ZIB), and Cl (CIB)), reversible Mg batteries (RMBs), dual-ion batteries (DIBs), Zn-air and Zn-sulphur batteries and supercapacitors as well as their relevance in other fields related to (opto)electronics. This selective panorama should help readers better understand the reason why ILCs are expected to meet the challenge of tomorrow as electrode materials.

Versatile Interplay of Chalcogenide and Dichalcogenide Anions in the Thiovanadate Ba7S(VS3O)2(S2)3 and Its Selenide Derivatives: Elaboration and DFT Meta-GGA Study

Oxychalcogenides are emerging as promising alternative candidates for a variety of applications including for energy. Only few phases among them show the presence of Q-Q bonds (Q = chalcogenide anion) while they drastically alter the electronic structure and allow further structural flexibility. Four original oxy(poly)chalcogenide compounds in the system Ba-V-Q-O (Q = S, Se) were synthesized, characterized, and studied using density functional theory (DFT). The new structure type found for Ba₇V₂O₂S₁₃, which can be written as Ba₇S(VS₃O)₂(S₂)₃, was substituted to yield three selenide derivatives Ba₇V₂O₂S_9.304Se_3.696, Ba₇V₂O₂S_7.15Se_5.85, and Ba₇V₂O₂S_6.85Se_6.15. They represent original multiple-anion lattices and first members in the system Ba-V-Se-S-O. They exhibit in the first layer heteroleptic tetrahedra V⁵⁺S₃O and isolated Q^2- anions and in the second layer dichalcogenide pairs (Q₂)^2- with Q = S or Se. Selenide derivatives were attempted by targeting the selective substitution of isolated Q^2- or (Q₂)^2- (in distinct layers) or both by selenide, but it systematically led to concomitant and partial substitution of both sites. A DFT meta-GGA study showed that selective substitution yields local constraints due to rigid VO₃S and pairs. Experimentally, incorporation of selenide in both layers avoids geometrical mismatch and constraints. In such systems, we show that the interplay between the O/S anionic ratio around V⁵⁺, together with the presence/nature of the dichalcogenides (Q₂)^2- and isolated Q^2-, impacts in unique manners the band gap and provides a rich background to tune the band gap and the symmetry.

Revisiting the Crystal Structure of Layered Oxychalcogenides Ln2O2S2 (Ln = La, Pr, and Nd)

La₂O₂S₂ was recently used as a precursor to prepare either a new metastable form of La₂O₂S by de-insertion of half of sulfur atoms of (S₂) dimers or quaternary compounds by insertion of a coinage metal (e.g., La₂O₂Cu₂S₂). A strong structural relationship exists between the polysulfide precursor and the synthesized products, which highlights the topochemical nature of these reactions. Nevertheless, the crystal structure of the precursor material is still a matter of debate. Namely, several structural models were reported so far in the literature with different space groups and/or crystal systems. All these models were built upon infinite [Ln₂O₂] slabs separated from each other by a flat sulfur layer of (S₂) dumbbells. Nevertheless, all (S₂) dimers within a given sulfur layer may rotate in phase by 90° compared to the ideal model that induces an overall atomic disorder in (S₂) dimer orientation along the stacking axis. This leads to some imbroglio and much confusion in the description of structural arrangement of Ln₂O₂S₂ materials. Herein, the crystal structures of La₂O₂S₂ and its Pr and Nd variants are revisited. We propose an alternative model that reconciles pre-existing structural descriptions of Ln₂O₂S₂ (Ln = La, Pr, and Nd) materials and highlights the strong dependency of the degree of long-range ordering of the sulfur layers on the synthesis conditions.

Structural Diversity of Rare-Earth Oxychalcogenides

Mixed-anion systems have garnered much attention in the past decade with attractive properties for diverse applications such as energy conversion, electronics, and catalysis. The discovery of new materials through mixed-cation and single-anion systems proved highly successful in the previous century, but solid-state chemists are now embracing an exciting design opportunity by incorporating multiple anions in compounds such as oxychalcogenides. Materials containing rare-earth ions are arguably a cornerstone of modern technology, and herein, we review recent advances in rare-earth oxychalcogenides. We discuss ternary rare-earth oxychalcogenides whose layered structures illustrate the characters and bonding preferences of oxide and chalcogenide anions. We then review quaternary compounds which combine anionic and cationic design strategies toward materials discovery and describe their structural diversity. Finally, we emphasize the progression from layered two-dimensional compounds to three-dimensional networks and the unique synthetic approaches which enable this advancement.

Solvothermal and mechanochemical intercalation of Cu into La2O2S2 enabled by the redox reactivity of (S2)2- pairs

Intercalation of Cu into layered polychalcogenide La₂O₂S₂ was demonstrated to be viable both under solvothermal conditions at 200 °C and mechanical ball milling at ambient temperature. This result evidences the soft-chemical nature of metal intercalation into layered polychalcogenides driven by the redox reactivity of anion-anion bonds.

Rank and signature classification of topochemical solid-state reactions

Solid-state reactions are classified into 10 categories based on the unit cells of the reactant and product.