Oxygen-defective V2O5 nanosheets boosting 3D diffusion and reversible storage of zinc ion for aqueous zinc-ion batteries

Aqueous zinc-ion batteries (ZIBs) have received considerable attention for reliable and low-cost energy storage. However, it remains a great challenge to develop cathode materials with high capacity and adequate cycle life due to the high polarization of bivalent Zn2+. Defect engineering has been demonstrated to enhance the electrochemical reaction sites but most defects are restricted to the surface of materials. We overcome this issue by incorporation of defect engineering and nanoengineering. Oxygen-defective V2O5 nanosheet arrays anchored on carbon cloth are employed as the cathode of ZIBs, which delivering comparable reversible capacity (322.9 and 256.6 at 1 and 5 A g−1) and stable cyclability (220 mAh g−1 after 500 cycles at 10 A g−1). Further DFT calculations validate that Zn2+ diffusion in oxygen-defective V2O5 is allowed along c axis, not only restricted along ab plane of V2O5, thus realizing a 3D Zn2+ diffusion with fast electrochemical kinetics and large capacitive storage. Moreover, the Zn2+ adsorption energies at defective sites of V2O5 was close to thermoneutral value, contributing reversible Zn2+ adsorption/desorption for ultra-stable Zn2+ storage performance. This synergistic strategy of defect engineering and nanoengineering reveal a promising potential for advanced materials of aqueous Zn-ion batteries and flexible storage applications.