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

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.