▎ 摘　　要

The exploration of anode materials with enhanced electronic/ionic conductivity and structural stability is beneficial for the development of sodium-ion batteries. Herein, a simple solution-derived method is demonstrated to fabricate porous VO2 microsphere composite with a graphene-wrapped structure (VO2/G). When used as the anode material for sodium-ion batteries, the VO2/G electrode delivers a high reversible specific capacity (373.0 mAhg(-1)), great rate capability (138.8 mAhg(-1) at 24.0 Ag-1, approximate to 21 s per charge/discharge), and excellent long-cycling performance (95.9% capacity retention for 3600 cycles at 2.0 Ag-1). The outstanding electrochemical property of VO2/G is mainly attributed to its unique graphene-wrapped porous structure and the pseudocapacitive-dominated feature. In addition, the sodium-ion storage mechanism of VO2/G is investigated by various ex-situ characterization techniques. During the first sodiation process, the sodium-ion appears to partially reduce VO2/G and form metallic vanadium, sodium oxide, and amorphous sodium vanadium. This work provides new fundamental information for the design and application of vanadium oxides for energy storage system.