Halide perovskite (HP) nanocrystals (NCs) have recently shown great potential for X-ray detection and imaging. However, the practical application is still a long way to go with lots of technical requirements waiting to be fulfilled, including structure optimization, stability enhancement, and cost reduction. A design principle in this beginning stage is urgently needed but still lacking. Herein, with an "emitter-in-matrix" principle refined from commercial scintillators, CsPbBr3@Cs4PbBr6 with emissive CsPbBr3 NCs embedded inside solid-state Cs4PbBr6 host is brought to X-ray sensing and imaging. The Cs4PbBr6 matrix not only enhances the attenuation of X-rays but also dramatically improves the stability of CsPbBr3 NCs. A favorable optical design with the Cs4PbBr6 matrix being transparent to the emission from CsPbBr3 NCs enables efficient light output. As a result, stable and sensitive scintillation response to X-ray signals is demonstrated with superior linearity and ultrahigh time resolution.In order to show the huge potential for practical application, X-ray imaging using a large-area film (360 mm×240 mm) by blade-coating technique is carried out to obtain a high-quality image of human eye-invisible interior structures. In addition to the above advantages in optics, CsPbBr3@Cs4PbBr6 also enjoys facile solution synthesis with large scalability, excellent repeatability and low cost.

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Sodium transition metal oxides with layered structures are attractive cathode materials for sodium-ion batteries due to their large theoretical specific capacities. However, these layered oxides suffer from poor cyclability and low rate performance because of structural instability and sluggish electrode kinetics. In the present work, we show the sodiation reaction of Mn3O4 to yield crystal water free NaMnO2−y−δ(OH)2y, a monoclinic polymorph of sodium birnessite bearing Na/Mn(OH)8 hexahedra and Na/MnO6 octahedra. With the new polymorph, NaMnO2−y−δ(OH)2y exhibits an enlarged interlayer distance of about 7 Å, which is in favor of fast sodium ion migration and good structural stability. In combination of the favorable nanosheet morphology, NaMn2−y−δ(OH)2y cathode delivers large specific capacity up to 211.9 mAh g–1, excellent cycle performance (94.6% capacity retention after 1000 cycles), and outstanding rate capability (156.0 mAh g–1 at 50 C). This study demonstrates an effective approach in tailoring the structural and electrochemical properties of birnessite towards superior cathode performance in sodium-ion batteries.

Metal‐organic frameworks (MOFs) are of quite a significance in the field of inorganic‐organic hybrid crystals. Especially, MOFs have attracted increasing attention in recent years due to their large specific surface area, desirable electrical conductivity, controllable porosity, tunable geometric structure, and excellent thermal/chemical stability. Some recent studies have shown that carbon materials prepared by MOFs as precursors can retain the privileged structure of MOFs, such as large specific surface area and porous structure and, in contrast, realize in situ doping with heteroatoms (eg, N, S, P, and B). Moreover, by selecting appropriate MOF precursors, the composition and morphology of the carbon products can be easily adjusted. These remarkable structural advantages enable the great potential of MOF‐derived carbon as high‐performance energy materials, which to date have been applied in the fields of energy storage and conversion systems. In this review, we summarize the latest advances in MOF‐derived carbon materials for energy storage applications. We first introduce the compositions, structures, and synthesis methods of MOF‐derived carbon materials, and then discuss their applications and potentials in energy storage systems, including rechargeable lithium/sodium‐ion batteries, lithium‐sulfur batteries, supercapacitors, and so forth, in detail. Finally, we put forward our own perspectives on the future development of MOF‐derived carbon materials.