Air-stability is one of the most important considerations for the practical application of electrode materials in energy-harvesting/storage devices, ranging from solar cells to rechargeable batteries. The promising P2-layered sodium transition metal oxides (P2-Na x TmO 2 ) often suffer from structural/chemical transformations when contacted with moist air. However, these elaborate transitions and the evaluation rules towards air-stable P2-Na x TmO 2 have not yet been clearly elucidated. Herein, taking P2-Na 0.67 MnO 2 and P2-Na 0.67 Ni 0.33 Mn 0.67 O 2 as key examples, we unveil the comprehensive structural/chemical degradation mechanisms of P2-Na x TmO 2 in different ambient atmospheres by using various microscopic/spectroscopic characterizations and first-principle calculations. The extent of bulk structural/chemical transformation of P2-Na x TmO 2 is determined by the amount of extracted Na + , which is mainly compensated by Na + /H + exchange. By expanding our study to a series of Mn-based oxides, we reveal that the air-stability of P2-Na x TmO 2 is highly related to their oxidation features in the first charge process and further propose a practical evaluating rule associated with redox couples for air-stable Na x TmO 2 cathodes.

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High-performance lithium-ion batteries are commonly built with heterogeneous composite electrodes that combine multiple active components for serving various electrochemical and structural functions. Engineering these heterogeneous composite electrodes toward drastically improved battery performance is hinged on a fundamental understanding of the mechanisms of multiple active components and their synergy or trade-off effects. Herein, we report a rational design, fabrication, and understanding of yolk@shell Bi 2 S 3 @N-doped mesoporous carbon (C) composite anode, consisting of a Bi 2 S 3 nanowire (NW) core within a hollow space surrounded by a thin shell of N-doped mesoporous C. This composite anode exhibits desirable rate performance and long cycle stability (700 cycles, 501 mAhg −1 at 1.0 Ag −1 , 85% capacity retention). By in situ transmission electron microscopy (TEM), X-ray diffraction, and NMR experiments and computational modeling, we elucidate the dominant mechanisms of the phase transformation, structural evolution, and lithiation kinetics of the Bi 2 S 3 NWs anode. Our combined in situ TEM experiments and finite element simulations reveal that the hollow space between the Bi 2 S 3 NWs core and carbon shell can effectively accommodate the lithiation-induced expansion of Bi 2 S 3 NWs without cracking C shells. This work demonstrates an effective strategy of engineering the yolk@shell-architectured anodes and also sheds light onto harnessing the complex multistep reactions in metal sulfides to enable high-performance lithium-ion batteries.

available online at http://meteoritics.org 269 Abstract-We describe the petrologic and trace element characteristics of the Yamato 86029 (Y-86029) meteorite. Y-86029 is a breccia consisting of a variety of clasts, and abundant secondary minerals including coarse-and fine-grained phyllosilicates, Fe-Ni sulfides, carbonates, and magnetite. There are no chondrules, but a few anhydrous olivine-rich grains are present within a very fine-grained phyllosilicate-rich matrix.Analyses of 14 thermally mobile trace elements suggest that Y-86029 experienced moderate, open-system thermal metamorphism. Comparison with data for other heated carbonaceous chondrites suggests metamorphic temperatures of 500-600ºC for Y-86029. This is apparent petrographically, in partial dehydration of phyllosilicates to incompletely re-crystallized olivine. This transformation appears to proceed through 'intermediate' highly-disordered 'poorly crystalline' phases consisting of newly formed olivine and residual desiccated phyllosilicate and their mixtures. Periclase is also present as a possible heating product of Mg-rich carbonate precursors.Y-86029 shows unusual textures rarely encountered in carbonaceous chondrites. The periclase occurs as unusually large Fe-rich clasts (300-500 µm). Fine-grained carbonates with uniform texture are also present as small (10-15 µm in diameter), rounded to sub-rounded 'shells' of ankerite/siderite enclosing magnetite. These carbonates appear to have formed by low temperature aqueous alteration at specific thermal decomposition temperatures consistent with thermodynamic models of carbonate formation. The fine and uniform texture suggests crystallization from a fluid circulating in interconnected spaces throughout entire growth. One isolated aggregate in Y-86029 also consists of a mosaic of polycrystalline olivine aggregates and sulfide blebs typical of shock-induced melt recrystallization.Except for these unusual textures, the isotopic, petrologic and chemical characteristics of Y-86029 are quite similar to those of Y-82162, the only other heated CI-like chondrite known. They were probably derived from similar asteroids rather than one asteroid, and hence may not necessarily be paired.

The mechanical properties of individual WS 2 nanotubes were investigated and directly related to their atomic structure details by in situ transmission electron microscope measurements. A brittle mode deformation was observed in bending tests of short (ca. 1 μm in length) multilayer nanotubes. This mode can be related to the atomic structure of their shells. In addition, longer nanotubes (6 7μm in length) were deformed in situ scanning electron microscope, but no plastic deformation was detected. A "sword-in-sheath" fracture mechanism was revealed in tensile loading of a nanotube, and the sliding of inner shells inside the outermost shell was imaged "on-line". Furthermore, bending modulus of 217 GPa was obtained from measurements of the electric-fi eldinduced resonance of these nanotubes.