Porous bowl-shaped VS2 nanosheets/graphene composite for high-rate lithium-ion storage

Two-dimensional (2D) layered vanadium disulfide (VS2) is a promising anode material for lithium ion batteries (LIBs) due to the high theoretical capacity. However, it remains a challenge to synthesize monodispersed ultrathin VS2 nanosheets to realize the full potential. Herein, a novel solvothermal method has been developed to prepare the monodispersed bowl-shaped NH3-inserted VS2 nanosheets (VS2). The formation of such a unique structure is caused by the blocked growth of (001) or (002) crystal planes in combination with a ripening process driven by the thermodynamics. The annealing treatment in Ar/H-2 creates porous monodispersed VS2 (H-VS2), which is subsequently integrated with graphene oxide to form porous monodispersed H-VS2/rGO composite coupled with a reduction process. As an anode material for LIBs, H-VS2/rGO delivers superior rate performance and longer cycle stability: a high average capacity of 868/525 mAh g(-1) at a current density of 1/10 A g(-1); a reversible capacity of 1177/889 mAh g(-1) after 150/500 cycles at 0.2/1 A g(-1). Such excellent electrochemical performance may be attributed to the increased active sites available for lithium storage, the alleviated volume variations and the shortened Li-ion diffusion induced from the porous structure with large specific surface area, as well as the protective effect from graphene nanosheets. (C) 2019 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.