Cobalt-Mediated Defect Engineering Endows High Reversible Amorphous VS 4 Anode for Advanced Sodium-Ion Storage.

Metal sulfides are promising anode materials for sodium-ion batteries (SIBs) due to their structural diversity and high theoretical capacity, but the severe capacity decay and inferior rate capability caused by poor structural stability and sluggish kinetics impede their practical applications. Herein, a cobalt-doped amorphous VS 4 wrapped by reduced graphene oxide (i.e., Co 0.5 -VS 4 /rGO) is developed through a Co-induced defect engineering strategy to boost the kinetics performances. The as-prepared Co 0.5 -VS 4 /rGO demonstrates excellent rate capacities over 10 A g -1 and superior cycling stability at 5 A g -1 over 1600 cycles, which is attributed to the defects formed by Co doping, the formed amorphous structure and the robust rGO substrate. The great features of Co 0.5 -VS 4 /rGO anode are further confirmed in sodium-ion capacitors when the active carbon cathode is used. Additionally, the relationships between metal doping, the derived defects, the amorphous structure, and the sodium storage of VS 4 are uncovered. This work provides deep insights into preparing amorphous functional materials and also probes the potential applications of metal sulfide-based electrode materials for advanced batteries.