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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.

Silicon-based anodes have the potential to be used in next-generation lithium ion batteries owing to their higher lithium storage capacity. However, the large volume change during the charge/discharge process and the repeated formation of a new solid electrolyte interface (SEI) on the re-exposed Si surface should be overcome to achieve a better electrochemical performance. Fluoroethylene carbonate (FEC) has been widely used as an electrolyte additive for Si-based anodes, but the intrinsical mechanism in performance improvement is not clear yet. Here, we combined solid-state NMR, X-ray photoelectron spectroscopy, and X-ray photoemission electron microscopy to characterize the composition, structure, and inhomogeneity of the SEI on Si/C composite anodes with or without the FEC additive. Similar species are observed with two electrolytes, but a denser SEI formed with FEC, which could prevent the small molecules (i.e., LiPF6, P–O, and Li–O species) from penetrating to the surface of the Si/C anode. The hydrolysis of LiPF6 leading to Li x PO y F z and further to Li3PO4 could also be partially suppressed by the denser SEI formed with FEC. In addition, a large amount of LiF could protect the cracking and pulverization of Si particles. This study demonstrates a deeper understanding of the SEI formed with FEC, which could be a guide for optimizing the Si-based anodes for lithium ion batteries.

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Sodium layered P2‐stacking Na0.67MnO2 materials have shown great promise for sodium‐ion batteries. However, the undesired Jahn–Teller effect of the Mn4+/Mn3+ redox couple and multiple biphasic structural transitions during charge/discharge of the materials lead to anisotropic structure expansion and rapid capacity decay. Herein, by introducing abundant Al into the transition‐metal layers to decrease the number of Mn3+, we obtain the low cost pure P2‐type Na0.67AlxMn1−xO2 (x=0.05, 0.1 and 0.2) materials with high structural stability and promising performance. The Al‐doping effect on the long/short range structural evolutions and electrochemical performances is further investigated by combining in situ synchrotron XRD and solid‐state NMR techniques. Our results reveal that Al‐doping alleviates the phase transformations thus giving rise to better cycling life, and leads to a larger spacing of Na+ layer thus producing a remarkable rate capability of 96 mAh g‐1 at 1200 mA g‐1.

Advanced spectroscopy methods quantitatively elucidate the failure process of lithium metal batteries.

In recent years solid Li + conductors with competitive ionic conductivity to those of liquid electrolytes have been reported. However, the incorporation of highly conductive solid electrolytes into the lithium-ion batteries is still very challenging mainly due to the high resistance existing at the solid-solid interfaces throughout the battery structure.Here, we demonstrated a universal interfacial modification strategy through coating a curable

Understanding the general electronic principles underlying molecule−surface interactions at the nanoscale is crucial for revealing the processes based on chemisorption, like catalysis, surface ligation, surface fluorescence, etc. However, the electronic mechanisms of how surface states affect and even dominate the properties of nanomaterials have long remained unclear. Here, using one-unit-thin TiO 2 nanosheet as a model surface platform, we find that surface ligands can competitively polarize and confine the valence 3d orbitals of surface Ti atoms from delocalized energy band states to localized chemisorption bonds, through probing the surface chemical interaction at the orbital level with near-edge X-ray absorption fine structure (NEXAFS). Such ligand-induced orbital redistributions, which are revealed by combining experimental discoveries, quantum calculations, and theoretical analysis, are cooperative with ligand coverages and can enhance the strength of chemisorption and ligation-induced surface effects on nanomaterials. The model and concept of nanoscale cooperative chemisorption reveal the general physical principle that drives the coverage-dependent ligand-induced surface effects on regulating the electronic structures, surface activity, optical properties, and chemisorption strength of nanomaterials.