Vanadium-driven oxygen vacancy modulation in MoO3 nanosheet cathodes for aqueous zinc-ion batteries

Abstract

Vanadium-doped MoO₃ (VMO) nanosheets with oxygen-vacancy-rich structures was synthesized via a hydrothermal route, where systematic control of doping concentration, reaction temperature, and time yielded nanosheet-stacked morphologies with enhanced surface area. The optimized sample, VMO (0.1 : 1), exhibited a specific surface area of 23.67 m² g⁻¹ and delivered a high reversible capacity of 213 mA h g⁻¹ at 1 A g⁻¹, together with excellent cycling stability, retaining 76% and 68% capacity after 2500 and 5000 cycles at 5 and 10 A g⁻¹, respectively. Ex situ characterization studies confirmed the coexistence of Zn²⁺ intercalation/deintercalation and H⁺ participation, with kinetic analyses revealing diffusion-controlled H⁺ storage and pseudocapacitive Zn²⁺ behavior. Moreover, density functional theory (DFT) calculations revealed that vanadium doping in MoO₃ reduces the bandgap, thereby enhancing electronic conductivity, and simultaneously lowers the Zn²⁺ migration barrier, facilitating ion transport. These results highlight vanadium doping as an effective strategy to enhance the electrochemical performance and structural stability of MoO₃, providing new insights into cathode design for advanced aqueous zinc-ion batteries.