Classical Li-ion battery technology is based on the insertion of lithium ions into cathode materials involving metal (cationic) redox reactions. However, this vision is now being reconsidered, as many new-generation electrode materials with enhanced reversible capacities operate through combined cationic and anionic (non-metal) reversible redox processes or even exclusively through anionic redox transformations. Anionic participation in the redox reactions is observed in materials with more pronounced covalency, which is less typical for oxides, but quite common for phosphides or chalcogenides. In this Concept, we would like to draw the reader's attention to this new idea, especially, as it applies to transition-metal polychalcogenides, such as FeS , VS , TiS , NbS , TiS , MoS , etc., in which the key role is played by the (S-S) /2 S redox reaction. The exploration and better understanding of the anion-driven chemistry is important for designing advanced materials for battery and other energy-related applications.

Large cavities occupied by cations and water molecules are part of the polymeric inorganic cluster structure made up of [Re6Se8(CN)6]4− and M2+ ions (M=Mn, Co; see structure on the right). Remarkably, the water molecules play an essential role in the stabilization of the structure: When the cluster is heated to 80–160°C, water is lost irreversibly, and a sharp change in structure is observed.

Hexadentate cluster anions [Re 6 S 8 (CN) 6 ] 42 coordinate to Mn(II) centers to give a neutral 3D coordination network topologically related to the structure of Prussian Blue; the residual space is filled with isopropyl alcohol molecules, both ligated to Mn(II) and guest-solvated.

Bulk NbS3and NbSe3were stably dispersed in a number of organic solvents to yield colloids containing thin well-crystallized nanoribbons of NbS3and NbSe3.