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Lattice-oxygen redox (l-OR) has become an essential companion to the traditional transition-metal (TM) redox charge compensation to achieve high capacity in Li-rich cathode oxides. However, the understanding of l-OR chemistry remains elusive, and a critical question is the structural effect on the stability of l-OR reactions. Herein, the coupling between l-OR and structure dimensionality is studied. We reveal that the evolution of the oxygen-lattice structure upon l-OR in Li-rich TM oxides which have a three-dimensional (3D)-disordered cation framework is relatively stable, which is in direct contrast to the clearly distorted oxygen-lattice framework in Li-rich oxides which have a two-dimensional (2D)/3D-ordered cation structure. Our results highlight the role of structure dimensionality in stabilizing the oxygen lattice in reversible l-OR, which broadens the horizon for designing high-energy-density Li-rich cathode oxides with stable l-OR chemistry.

The efficient conversion and storage of solar energy for chemical fuel production presents a challenge in sustainable energy technologies. Metal nitrides (MNs) possess unique structures that make them multi‐functional catalysts for water splitting. However, the thermodynamic instability of MNs often results in the formation of surface oxide layers and ambiguous reaction mechanisms. Herein, we present on the photo‐induced reconstruction of a Mo‐rich@Co‐rich bi‐layer on ternary cobalt‐molybdenum nitride (Co3Mo3N) surfaces, resulting in improved effectiveness for solar water splitting. During a photo‐oxidation process, the uniform initial surface oxide layer is reconstructed into an amorphous Co‐rich oxide surface layer and a subsurface Mo−N layer. The Co‐rich outer layer provides active sites for photocatalytic oxygen evolution reaction (POER), while the Mo‐rich sublayer promotes charge transfer and enhances the oxidation resistance of Co3Mo3N. Additionally, the surface reconstruction yields a shortened Co−Mo bond length, weakening the adsorption of hydrogen and resulting in improved performance for both photocatalytic hydrogen evolution reaction (PHER) and POER. This work provides insight into the surface structure‐to‐activity relationships of MNs in solar energy conversion, and is expected to have significant implications for the design of metal nitride‐based catalysts in sustainable energy technologies. [ABSTRACT FROM AUTHOR]

Halide solid electrolytes (SEs) have attracted significant attention due to their competitive ionic conductivity and good electrochemical stability. Among typical halide SEs (chlorides, bromides, and iodides), substantial efforts have been dedicated to chlorides or bromides, with iodide SEs receiving less attention. Nevertheless, compared with chlorides or bromides, iodides have both a softer Li sublattice and lower reduction limit, which enable iodides to possess potentially high ionic conductivity and intrinsic anti‐reduction stability, respectively. Herein, we report a new series of iodide SEs: LixYI3+x (x=2, 3, 4, or 9). Through synchrotron X‐ray/neutron diffraction characterizations and theoretical calculations, we revealed that the LixYI3+x SEs belong to the high‐symmetry cubic structure, and can accommodate abundant vacancies. By manipulating the defects in the iodide structure, balanced Li‐ion concentration and generated vacancies enables an optimized ionic conductivity of 1.04 × 10−3 S cm−1 at 25 °C for Li4YI7. Additionally, the promising Li‐metal compatibility of Li4YI7 is demonstrated via electrochemical characterizations (particularly all‐solid‐state Li‐S batteries) combined with interface molecular dynamics simulations. Our study on iodide SEs provides deep insights into the relation between high‐symmetry halide structures and ionic conduction, which can inspire future efforts to revitalize halide SEs. [ABSTRACT FROM AUTHOR]