The high theoretical gravimetric capacity of the Li–S battery system makes it an attractive candidate for numerous energy storage applications. In practice, cell performance is plagued by low practical capacity and poor cycling. In an effort to explore the mechanism of the discharge with the goal of better understanding performance, we examine the Li–S phase diagram using computational techniques and complement this with an in situ ⁷Li NMR study of the cell during discharge. Both the computational and experimental studies are consistent with the suggestion that the only solid product formed in the cell is Li₂S, formed soon after cell discharge is initiated. In situ NMR spectroscopy also allows the direct observation of soluble Li⁺-species during cell discharge; species that are known to be highly detrimental to capacity retention. We suggest that during the first discharge plateau, S is reduced to soluble polysulfide species concurrently with the formation of a solid component (Li₂S) which forms near the beginning of the first plateau, in the cell configuration studied here. The NMR data suggest that the second plateau is defined by the reduction of the residual soluble species to solid product (Li₂S). A ternary diagram is presented to rationalize the phases observed with NMR during the discharge pathway and provide thermodynamic underpinnings for the shape of the discharge profile as a function of cell composition.

Metal-doped polyoxotitanium cages (M-POTs) of the type [Ti_xO_y(OR)_zM_nX_m] (M = a main group, transition metal or lanthanide; X = an anion such as a halide) can be regarded as molecular fragments of metal-doped TiO₂. As such M-POTs can be used as structural models for the inclusion of metal ions into the TiO₂ lattice and the ways in which well-defined microstructural changes affect photo-induced hole–electron separation. They are also potential organically-soluble redox-catalysts for a range of organic transformations and have been shown to be useful single-source precursors for the deposition of metal-doped TiO₂. The applications of M-POTs as molecular precursors to metal-doped TiO₂ offers a high degree of atomic control in the low temperature fabrication of photocatalytic thin films, which have applications in pollution control and water splitting. This perspective highlights the structural trends in M-POTs, their electronic behaviour and their applications as single-source precursors, looking at current and future trends in the development of inorganic precursors for device applications.

Functional ligand-modified polyoxotitanate (L-POT) cages of the general type [Ti_xO_y(OR)_z(L)_m] (OR = alkoxide, L = functional ligand) can be regarded as molecular fragments of surface-sensitized solid-state TiO₂, and are of value as models for studying the interfacial charge and energy transfer between the bound functional ligands and a bulk semiconductor surface. These L-POTs have also had a marked impact in many other research fields, such as single-source precursors for TiO₂ deposition, inorganic–organic hybrid material construction, photocatalysis, photoluminescence, asymmetric catalysis and gas adsorption. Their atomically well-defined structures provide the basis for the understanding of structure/property relationships and ultimately for the rational design of new cages targeting specific uses. This highlight focuses on recent advances in L-POTs research, with emphasis on their novel properties and potential applications.

Transition metal chalcogenides are an important family of materials that have received significant interest in recent years as they have the potential for diverse applications ranging from use in electronics to industrial lubricants.

This perspective summarises the key synthetic routes to iron chalcogenide thin films/nanoparticles by highlighting the key aspects that lead to control over phase/morphology.