Ultrastable hydrated vanadium dioxide cathodes for high-performance aqueous zinc ion batteries with H+/Zn2+ Co-insertion mechanism

Abstract

Aqueous zinc-ion batteries (AZIBs) based on high-safety zinc metal anodes have advantages of low cost and high theoretical capacity and are considered as a promising large-scale energy storage system. Their practical application, however, is hampered by slow transport kinetics, low energy density, and poor cycling performance. In this work, we design and successfully synthesize ultrastable lattice water-rich VO₂·xH₂O materials by considering the fact that abundant crystallized water can act as “water lubrication”, and a charge shielding medium to weaken the electrostatic effect. As a result, VO₂·xH₂O as a cathode for AZIBs can provide a specific capacity of 376 mA h g⁻¹ after 200 cycles at 1 A g⁻¹ and no apparent capacity decay after 8000 cycles at 15 A g⁻¹. The excellent zinc storage performance can be ascribed to the efficient kinetics and abundant reaction sites of the VO₂·xH₂O electrode. A series of in situ and ex situ characterizations indicate that it is the H⁺/Zn²⁺ co-intercalation mechanism to store zinc in the VO₂·xH₂O electrode. In short, the abundant crystallized water vanadium-based materials may be excellent candidates for advanced cathode materials of AZIBs.