Electrochemically inducing V2O5·nH2O nanoarrays vertically growth on VSx microrods for highly stable zinc ion battery cathode

Abstract

The lack of suitable cathode materials greatly limits the potential applications of rechargeable aqueous zinc ion batteries (ZIBs), despite their great promise in terms of high safety, high energy density, and low cost. One promising cathode material is VOOH, which possesses high specific capacity and fast Zn2+ transport channels after a phase transition to V2O5·nH2O during electrochemical cycling. However, its susceptibility to structural disintegration and aggregation during charging and discharging leads to severe capacity decay. To address this issue, we construct a composite consisting of VOOH particles and VSx microrods by a one-step hydrothermal method using a vanadium-based metal-organic framework (MIL-88B(V)) as a sacrificial template. The VOOH particles undergo electrochemical activation and transform into V2O5·nH2O nanoarrays that vertically grow on the VSx microrods. This unique nano-composite effectively maintains the morphology of nanoarrays in electrochemical cycling, resulting in a significant enhancement of rate performance and long-term cycling stability. Moreover, the VSx itself provides considerable capacity and its high conductivity improves the rate performance of the composite. Consequently, the VOOH/VSx nanocomposite exhibits a superior capacity of 364 mA h g−1 at 0.2 A g−1 after activation. Notably, it maintains remarkable capacity retention of 99.6% after 700 cycles, even at a high current density of 10 A g−1. Based on these findings, we believe that the VOOH/VSx composite holds great promise as a cathode material for aqueous ZIBs.