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

Thanks to low cost and high safety, aqueous zinc-ion batteries (AZIBs) are attractive candidates for largescale energy storage applications, while suitable cathode materials are needed urgently. In this work, delta-NaxV2O5 center dot nH(2)O with a large interlayer spacing of 10.6 angstrom is reported as the cathode material for aqueous zinc-ion batteries for the first time. It is found that delta-NaxV2O5 center dot nH(2)O performs better than Na2V6O16 center dot nH(2)O 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 delta-NaxV2O5 center dot nH(2)O 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/delta-NaxV2O5 center dot nH(2)O nanocomposite. This work extends the knowledge into the material technology of AZIBs. (C) 2019 Elsevier Ltd. All rights reserved.