Amorphous Vanadium Oxide Nanosheets with Alterable Polyhedron Configuration for Fast‐Charging Lithium‐Ion Batteries

Abstract

AbstractTransition metal oxides with high theoretical capacities are promising anode materials for lithium‐ion batteries (LIBs). However, the sluggish reaction kinetics remain a bottleneck for fast‐charging applications due to its slow Li+ migration rate. Herein, a strategy is reported of significantly reducing the Li+ diffusion barrier of amorphous vanadium oxide by constructing a specific ratio of the VO local polyhedron configuration in amorphous nanosheets. The optimized amorphous vanadium oxide nanosheets with a ratio ≈1:4 for octahedron sites (Oh) to pyramidal sites (C4v) revealed by Raman spectroscopy and X‐ray absorption spectroscopy (XAS) demonstrate the highest rate capability (356.7 mA h g−1 at 10.0 A g−1) and long‐term cycling life (455.6 mA h g−1 at 2.0 A g−1 over 1200 cycles). Density functional theory (DFT)calculations further verify that the local structure (Oh:C4v = 1:4) intrinsically changes the degree of orbital hybridization between V and O atoms and contributes to a higher intensity of electron occupied states near the Fermi level, thus resulting in a low Li+ diffusion barrier for favorable Li+ transport kinetics. Moreover, the amorphous vanadium oxide nanosheets possess a reversible VO vibration mode and volume expansion rate close to 0.3%, as determined through in situ Raman and in situ transmission electron microscopy.