Tailoring Energy and Power Density through Controlling the Concentration of Oxygen Vacancies in V₂O₅/PEDOT Nanocable-Based Supercapacitors

Abstract

Oxygen vacancies (Vö) play a crucial role in energy storage materials. Oxygen-vacancy-enriched vanadium pentoxide/poly(3,4-ethylenedioxythiophene) (Vö-V₂O₅/PEDOT) nanocables were prepared through the one-pot oxidative polymerization of PEDOT. PEDOT is used to create tunable concentrations of Vö in the surface layer of V₂O₅, which has been confirmed by X-ray absorption near edge structure (XANES) analysis and X-ray photoelectron spectroscopy (XPS) measurements. Applied as electrode materials for supercapacitors, the electrochemical performance of Vö-V₂O₅/PEDOT is improved by the synergistic effects of Vö in V₂O₅ cores and PEDOT shells with rapid charge transfer and fast Na⁺ ion diffusion; however, it is compromised subsequently by excessive Vö in consuming more V⁵⁺ cations for Faradic reactions. Consequently, the specific capacitance and the energy density of Vö-V₂O₅/PEDOT nanocables are significantly enhanced when the overall concentration of Vö is 1.3%. The migration of Vö renders an increased capacitance (105% retention) after 10 000 cycles, which is verified and corroborated with density functional theory simulations and XANES analysis. This work provides an illumination for the fabrication of high-performance electrode materials in the energy storage field through Vö.