Synergistic co-intercalation of binary and ternary transition-metal cations in hydrated vanadium oxide nanosheets for high-performance aqueous zinc-ion batteries

Abstract

Vanadium-based oxides have emerged as promising cathode materials in aqueous zinc-ion batteries (AZIBs), owing to their tunable layered architectures and high theoretical specific capacities. To date, hydrothermal/solvothermal synthesis remains the predominant approach for preparing vanadium-based oxides. However, the aforementioned approaches face substantial challenges in achieving precise control over microstructural morphology. In this work, we developed a novel hydrosol ionic self-assembly synthesis strategy. Using V 2 O 5 ∙nH 2 O hydrosol as the precursor, followed by dropwise addition of multicomponent ion mixed solutions containing Co 2+ /Ni 2+ , Co 2+ /Cu 2+ , Ni 2+ /Cu 2+ , and Co 2+ /Ni 2+ /Cu 2+ , four binary and ternary transition-metal cations synergistically intercalated V 2 O 5 ∙nH 2 O nanosheets were synthesized and denoted as CN-VOH, CC-VOH, NC-VOH, and CNC-VOH, respectively. Electrochemical measurements demonstrate that the CNC-VOH cathode delivers a superior specific discharge capacity of 338.9 mA h g −1 at a current density of 0.05 A g −1 . Specially, the CNC-VOH cathode, benefiting from the synergistic intercalation of Co 2+ , Ni 2+ , and Cu 2+ , delivers exceptional long-term cycling stability, maintaining stable operation over 5000 cycles at a current density of 5 A g −1 . Density functional theory (DFT) calculations reveal that the synergistic intercalation of Co 2+ , Ni 2+ , and Cu 2+ introduces additional 3d electronic states, strengthens orbital hybridization, enhances the electronic density of states (DOS) near the Fermi level of pristine V 2 O 5 , and narrows the band gap, thereby improving the electronic conductivity and charge transfer kinetics of the material.