Strengthening the Interface between Flower-Like VS4 and Porous Carbon for Improving Its Lithium Storage Performance

Carbon materials are frequently used to improve the cycle and rate performance of VS4 as anode material for lithium ion batteries. However, the interfacial interaction between VS4 and carbon has not been elucidated clearly. Various VS4@C composites are prepared and the interface between VS4 and porous carbon is investigated by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, and first-principles calculations. The interfacial structure between VS4 and carbon and the mechanism of flower-like VS4 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 VS4@C composite. Deriving from the unique structure and robust interfacial interaction, the electrochemical performances of VS4@C composite are much better than that of pure VS4. Moreover, through the study of lithium storage mechanism of VS4 anode, it is found that there is an irreversible amorphization change of the original VS4 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 VS4 with the reaction between V4+ and V3+.