Dual ions pre-intercalated hydrate vanadium oxide as cathode drives high-performance aqueous zinc ions storage

Rechargeable aqueous zinc ion batteries (ZIBs) are promising energy storage devices due to high safety and low cost in recent years. However, the cathode materials faced the challengeable problems like the dissolution of cathode materials, degradation of specific capacity and so on. Herein, Na ions and Mg ions pre-intercalated vanadium oxide denoted as Na_0.56Mg_0.28V₅O₁₂·2.6 H₂O with large interlayer spacing of 13.26 Å and robust porous structure was synthesized by one-step hydrothermal method and showed outstanding Zn-storage performance. The as-synthesized cathode delivered excellent specific capacity of 490 mA h g⁻¹ at 0.1 A g⁻¹, and exhibited superior stability of 70% retention after 4000 cycles at 10 A g⁻¹. More importantly, ex-situ XRD, XPS and SEM techniques were used to explore the possible Zn-storage mechanism of this cathode in the initial two discharge/charge cycles. This Na⁺ and Mg²⁺ co-inserted vanadium oxide cathode provides an effective pre-intercalated strategy to improve electrochemical performance of ZIBs.