Synergistic effects in V3O7/V2O5 composite material for high capacity and long cycling life aqueous rechargeable zinc ion batteries

Zinc ion batteries (ZIBs) have great competitiveness in large-scale energy storage because of their low price, environmental friendliness, safety and efficiency. In this work, we study a composite material of V3O7/V2O5 as the cathode in ZIBs. Owing to the synergistic effects of V3O7 and V2O5, it presents an excellent zinc ion storage performance including high cyclic stability with capacity retention of 96.2% after 1120 cycles (1000 cycles after activation) at 2 A g−1, excellent rate capability with specific discharge capacity of 176 mA h g−1 at 5 A g−1 and long circle life with 17.4% capacity fading after 6500 cycle. In addition, the battery offers a high energy density of 271 W h kg−1 at 0.2 A g−1 and a high power density of 3220 W kg−1 at 5 A g−1 (based on the cathode and the theoretically required of Zn anode). The synergistic effect is confirmed by a series structural and electrochemical characterization that the interaction of V2O5 and V3O7 can promote the vanadium valence change from Ⅴ (or Ⅳ) to Ⅲ. This work provides a promising cathode material with high capacity and long cycling stability, which will have a great advantage and prospect in the large-scale energy storage.