A distinctive conversion mechanism for reversible zinc ion storage

Abstract

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 V₂O₅·3H₂O under high-voltage conditions. The reconstructed phase (V₂O₅·3H₂O) 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 V₂O₅·3H₂O and Zn₃V₂O₇(OH)₂·2H₂O (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.