VS 4 Nanoparticles Anchored on Graphene Sheets as a High-Rate and Stable Electrode Material for Sodium Ion Batteries.

The size and conductivity of the electrode materials play a significant role in the kinetics of sodium-ion batteries. Various characterizations reveal that size-controllable VS4 nanoparticles can be successfully anchored on the surface of graphene sheets (GSs) by a simple cationic-surfactant-assisted hydrothermal method. When used as an electrode material for sodium-ion batteries, these VS4 @GS nanocomposites show large specific capacity (349.1 mAh g-1 after 100 cycles), excellent long-term stability (84 % capacity retention after 1200 cycles), and high rate capability (188.1 mAh g-1 at 4000 mA g-1 ). A large proportion of the capacity was contributed by capacitive processes. This remarkable electrochemical performance was attributed to synergistic interactions between nanosized VS4 particles and a highly conductive graphene network, which provided short diffusion pathways for Na+ ions and large contact areas between the electrolyte and electrode, resulting in considerably improved electrochemical kinetic properties.