Multi-metal ions co-regulated vanadium oxide cathode toward long-life aqueous zinc-ion batteries

Interlayer intercalation engineering shows great feasibility to improve the structure stability of the layered oxides. Although high Zn-storage capability has been attained based on the pillar effect of multifarious intercalants, an in-depth understanding the synergistic effect of intercalated multiple metal ions is still in deficiency. Herein, alkali metal ion K⁺, alkaline earth metal ion Mg²⁺ and trivalent metal ion Al³⁺ are introduced into the VO interlayer of V₂O₅. Due to the different electronegativity and hydrated ion radius of K⁺, Mg²⁺ and Al³⁺, adjusting the relative proportions of these metal ions can achieve an appropriate interlayer spacing, stable layer structure and regular morphology, which facilitates the transport kinetics of Zn²⁺. Under the synergistic effect of pre-intercalated multi-metal ion, the optimal tri-metal ion intercalated hydrated V₂O₅ cathode exhibits a high specific capacity of 382.4 mAh g^-1 at 0.5 A g^-1, and long-term cycling stability with capacity retention of 86 % after 2000 cycles at the high current density of 10 A g^-1. Ex-situ and kinetic characterizations reveal the fast charge transfer and reversible Zn²⁺ intercalation mechanism. The multi-ion engineering strategy provides an effective way to design desirable layered cathode materials for aqueous zinc-ion batteries.