Facile synthesis of tetragonal NaV2O5·H2O nanosheets co-intercalated by high content of Na+ and H2O for boosted lithium storage

Abstract

NaxV2O5·yH2O have been considered to be very promising electrode materials in the energy storage field by virtue of their V4+/V5+ mixed valences and co-intercalated Na+/H2O. However, the as-reported NaxV2O5·yH2O usually present the low content of Na+ and the anisotropy of Li+ diffusion in the plane direction. Herein, we successfully synthesize a tetragonal NaV2O5·H2O nanosheets co-intercalated by high content of Na+ and H2O via a simple one-step hydrothermal method under broad synthesis conditions, where S2- reductant has been proved to bevery significantforits successful synthesis. With the synergistic effect of the isotropy of tetragonal lattice in the plane direction, and the co-intercalated high content of Na+ and H2O, NaV2O5·H2O nanosheets as anode material for lithium-ion batteries exhibit excellent electrochemical performance. The initial discharge and charge capacities are up to 859 and 607 mA h g−1 at 100 mA g−1, and the capacity is maintained at 473 mA h g−1 after 500 cycles, which are outperform other reported layered sodium/lithium vanadate, lithium titanate, lithium/titanium niobate and graphite. In addition, we also reveal that the active material during cycling process is the LixNayV2O5·H2O with stable crystal structure and morphology, and the Li+ storage process is coequally determined by diffusion and pseudocapacitive behavior.