Hybridizing δ-type NaxV2O5·nH2O with graphene towards high-performance aqueous zinc-ion batteries

Abstract

Thanks to low cost and high safety, aqueous zinc-ion batteries (AZIBs) are attractive candidates for large-scale energy storage applications, while suitable cathode materials are needed urgently. In this work, δ-NaxV2O5·nH2O with a large interlayer spacing of 10.6 Å is reported as the cathode material for aqueous zinc-ion batteries for the first time. It is found that δ-NaxV2O5·nH2O performs better than Na2V6O16·nH2O under the same condition, and its electrochemical performances can be significantly improved after hybridizing it with reduced graphene oxide. The obtained nanocomposite can deliver high reversible capacity of 433.5 mAh g−1 at 0.1 A g−1, superior rate capability of 244.1 mAh g−1 at 5 A g−1, and good cyclability of 70.5% over 1000 cycles. Such great performances origin from the synergetic effect of δ-NaxV2O5·nH2O and graphene, which enables rapid Zn2+ diffusion and large capacitive contribution. Besides, the ex-situ measurement results demonstrate good structural stability and reversible Zn2+ ion storage behavior of reduced graphene oxide/δ-NaxV2O5·nH2O nanocomposite. This work extends the knowledge into the material technology of AZIBs.