Heteroatom doping hollow vanadium oxide/carbon composites as universal anode materials for efficient alkali-metal ion storage

Hollow structure and heteroatom doping strategies are effective approaches to prepare high-performance energy storage materials. Herein, hollow precursors are obtained in a solvothermal reaction based on Ostwald-ripening process, time-tracking and variable-control methods are adopted to explore the formation mechanism and influencing factors of hollow precursors. Selenium-doped V₂O₃/carbon composites (VO_Se) are prepared via the high-temperature selenization process. VO_Se manifests abundant internal space and plentiful defects, which provides more adsorption sites for Na⁺/K⁺/Li⁺ and facilitates immersion of the electrolyte. Therefore, VO_Se exhibits a higher capacity and excellent cycle stability for sodium storage (201.5 mA h/g after 2700 cycles at 3.0 A/g), potassium storage (162.3 mA h/g after 500 cycles at 0.5 A/g) and lithium storage (305 mA h/g at 5.0 A/g over 1000 cycles), Compared to V₂O₃/carbon composites (VO), kinetic analysis and DFT calculation indicate that VO_Se possesses more rapid Na ⁺ diffusion kinetics and lower diffusion barrier. The reversible chemical transformation of Na⁺+V₂O₃ ↔ α-NaVO₃ and performance evolution are characterized via ex-situ analyses. Finally, full-cells assembled with Na₃V₂(PO₄)₃ cathode exhibits superior cycle stability (170.8 mA h/g after 150 cycles at 0.5 A/g).