Diglyme-based electrolytes boosting high-rate and stable sodium-ion storage for three-dimensional VS4/Reduced graphene oxide hybrid anodes

VS4 as a promising anode material for sodium ion batteries (SIBs), has attracted great attention due to its large interchain distance of 5.83 angstrom. However, the reported VS4 anodes always show a low capacity and unstable cycling performance. Herein, a three-dimensional (3D)-VS4/reduced graphene oxide (rGO) hybrid (denoted 3D-VS4/rGO) has been prepared, having a structure of VS4 nanorods (85.8 wt%) uniformly anchored to flexible graphene sheets to form a 3D hierarchical framework. It is interesting found that such anode shows superior electrochemical performance with excellent rate capability (700 mAh g(-1) at 5 A g(-1)) and long cyclic stability (587 mAh g(-1) over 400 cycles at 5 A g(-1) ) in 1 M NaPF6 diglyme-based electrolyte, much better than the performance in 1 M NaCF3SO3 diglyme-based electrolyte. The simulation results reveal that the different coordination shell structure of Na+ of different sodium salts in the electrolyte is the main reason for the performance differences, and a smaller solvation shell of Na+ -solvent in NaPF6 rather than that of Na -anion-solvent in NaCF3SO3 led to the fast reaction kinetics in the sodiation/desodiation process, showing the importance of electrode and electrolyte matching in improving the electrochemical performance of SIBs.