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 Mg and trivalent metal ion Al are introduced into the VO interlayer of VO. Due to the different electronegativity and hydrated ion radius of K, Mg and Al, 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 Zn. Under the synergistic effect of pre-intercalated multi-metal ion, the optimal tri-metal ion intercalated hydrated VO cathode exhibits a high specific capacity of 382.4 mAh g at 0.5 A g, and long-term cycling stability with capacity retention of 86 % after 2000 cycles at the high current density of 10 A g. Ex-situ and kinetic characterizations reveal the fast charge transfer and reversible Zn intercalation mechanism. The multi-ion engineering strategy provides an effective way to design desirable layered cathode materials for aqueous zinc-ion batteries.