Mechanism enhancement of V3O7/V6O13 heterostructures to achieve high-performance aqueous Zn-Ion batteries

Vanadium oxides are the most promising cathode materials for aqueous Zn-ion batteries (AZIBs). A major restriction of vanadium oxides in practical applications is their poor utilization due to the limited migration depth of Zn2+. Mechanism enhancement through modifying Zn2+ intercalation chemistry is the key to boost the performance of vanadium oxides, but yet has rarely been reported. Through a series of ex situ characterizations, we demonstrate here a new two-process reversible transition mechanism in V3O7/V6O13 heterostructures. We observe an unusual reversible transition between V3O7/V6O13 and Zn3V2O7(OH)2·2H2O (ZVO, also a known Zn2+ and proton intercalation material), both of which can be the active materials for subsequent energy storage. This suggests that the Zn2+ intercalation pressure can be shared by the two hosts at deep discharging, that is, the active materials may be better utilized as compared to the only host, which is conducive to improving the available capacity. In addition, the generated ZVO also aids in Zn2+/H+ diffusion due to its open layered structure and water-lubricated channels. With the advanced energy storage mechanism, 2D defective heterostructures, and a facile and energy-efficient synthesis, the V3O7/V6O13 nanosheets are expected to be a high-performance and mass-produced cathode material for commercial AZIBs.