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In the spinel oxide cathode family, LiNi0.5Mn1.5O4 (LNMO) shows a high operating voltage (≈4.7 V vs Li/Li+) and excellent Li‐ion mobility with stable 3D conducting channels. Ni/Mn cation disordered and ordered phases usually coexist in LNMO materials, and they have distinct structural and electrochemical properties, resulting in different battery performances for LNMO materials with different phase compositions. Identifying the correlation between phase compositions and electrochemical properties is of significance to the improvement of battery performance and understanding of degradation mechanisms. Herein, the disordered/ordered phase compositions in LNMO materials are tailored by post‐annealing strategies and their impacts on electrochemical performance and degradation mechanisms from the surface to the bulk are systematically investigated. The ordered phase increases rapidly as Mn3+ is oxidized to Mn4+ through a post‐annealing process. LNMO with an intermediate fraction of disordered and ordered phases gives rise to improved cycling stability. This article further reports that a high ordered phase fraction can preferentially protect Ni from dissolution during cycling. However, these results suggest that the transition metal dissolution and surface structural change of LNMO do not exhibit a direct correlation with cycling stability. These results indicate the capacity fading mainly correlates with the bulk structural distortion, leading to decreased Li‐ion kinetics. [ABSTRACT FROM AUTHOR]

Use of amorphous precursors is a widespread strategy in biomineralization. In sea urchin embryos, controlled transformation of amorphous calcium carbonate (ACC) to calcite results in smoothly curving and branching single crystals. However, the mechanism of the disorder-to-order transformation remains poorly understood. Here, the use of strontium as a probe in X-ray absorption spectroscopy (XAS) greatly facilitates investigation of the evolution of order. In pulse-chase experiments, embryos incorporate Sr2+ from Sr-enriched seawater into small volumes of the growing endoskeleton. During the chase, the Sr-labeled mineral matures under physiological conditions. Based on Sr K-edge spectra of cryo-frozen whole embryos, it is proposed that the transformation occurs in three stages. The initially deposited calcium carbonate has short-range order resembling synthetic hydrated ACC. Within 3 h, the short-range order of calcite is established. Between 3 h and 24 h, the short-range order does not change, while long-range order increases. These results refute the notion that organisms imprint the local order of the final crystal on ACC. Furthermore, it is proposed that the intermediate is more similar to disordered calcite than to anhydrous ACC. Pulse-chase experiments in conjunction with heavy element labeling have great potential to improve understanding of phase transformations during biomineralization. [ABSTRACT FROM AUTHOR]

Developing novel one-dimensional (1D) luminescent nanostructures (e.g., nanowires and nanoribbons) is highly desired for enabling progress in nanophotonics and other emerging optical technologies. Previous studies on 1D luminescent nanostructures were mostly focused on elemental and binary semiconductor materials, the light emission of which originates from the radiative recombination of electrons and holes via either intrinsic states or extrinsic defect states. Herein, three kinds of ternary europium aluminate nanoribbons are reported that have localized Eu2+ luminescent centers and exhibit new compositions, new crystal lattice structures, and new luminescence properties and mechanisms. These three europium aluminate nanoribbons are: blue luminescent EuAl6O10 with a new composition and a new tetragonal lattice structure, green luminescent EuAl2O4 with a monoclinic lattice structure, and orange luminescent EuAl2O4 with a new hexagonal lattice structure and extremely large band width and Stokes shift of emission. These materials have promising applications as nanometer-scale light generators and waveguides in nanophotonics and as light converting phosphors in warm white light-emitting diodes. [ABSTRACT FROM AUTHOR]