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In situ synthesized oxygen vacancy-enriched MoO3−x nanobelts realized excellent electrochemical performance as asymmetric supercapacitors at room/low temperature.

Carbon materials are frequently used to improve the cycle and rate performance of VS 4 as anode material for lithium ion batteries. However, the interfacial interaction between VS 4 and carbon has not been elucidated clearly. Various VS 4 @C composites are prepared and the interface between VS 4 and porous carbon is investigated by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, and first-principles calculations. The interfacial structure between VS 4 and carbon and the mechanism of flower-like VS 4 growth on carbon substrate are revealed clearly. The results indicate that C−V bonds and C−O−V bonds are formed when oxygen functional groups are introduced into the porous carbon, and the C−V bonds and C−O−V bonds accelerate the electron transport and enhance structural stability of the VS 4 @C composite. Deriving from the unique structure and robust interfacial interaction, the electrochemical performances of VS 4 @C composite are much better than that of pure VS 4 . Moreover, through the study of lithium storage mechanism of VS 4 anode, it is found that there is an irreversible amorphization change of the original VS 4 in the first cycle, and that during the following electrochemical process, the main storage behavior of lithium ions derives from the insertion−extraction reactions in the amorphous VS 4 with the reaction between V 4+ and V 3+ .