A distinctive conversion mechanism for reversible zinc ion storage

For a long time, in aqueous zinc-ion batteries, the intercalation/extraction chemistry of Zn2+/H+ has been considered as the primary energy storage mechanism in vanadium-based compounds. Herein, we observed an interesting phase transition of V2O3 to V2O5 center dot 3H(2)O under high-voltage conditions. The reconstructed phase (V2O5 center dot 3H(2)O) displays an improved specific capacity of 472.4 mA h g(-1), about 5 times larger than that of the original compound (V2O3). What's more, the electrode exhibits a highly reversible conversion reaction between V2O5 center dot 3H(2)O and Zn3V2O7(OH)(2)center dot 2H(2)O (ZVO) during the charge/discharge process, showing an excellent rate capability and cycling stability. The findings also confirm the electrochemical activity of ZVO, which has generally been considered to be an inactive by-product. This energy storage mechanism, different from the previously reported intercalation chemistry, offers a new insight to understand the electrochemical behavior of V-based electrode materials.